Olympus Mons on Mars is the largest volano in our Solar System. Analysis of a Martian meteorite that fell to Earth in 2012 confirms that Mars also has the longest-lived volcanoes in our Solar System. Image: NASA/JPL
Mars is renowned for having the largest volcano in our Solar System, Olympus Mons. New research shows that Mars also has the most long-lived volcanoes. The study of a Martian meteorite confirms that volcanoes on Mars were active for 2 billion years or longer.
A lot of what we know about the volcanoes on Mars we’ve learned from Martian meteorites that have made it to Earth. The meteorite in this study was found in Algeria in 2012. Dubbed Northwest Africa 7635 (NWA 7635), this meteorite was actually seen travelling through Earth’s atmosphere in July 2011.
A sample from the meteorite Northwest Africa 7635. Image: Mohammed Hmani
The lead author of this study is Tom Lapen, a Geology Professor at the University of Houston. He says that his findings provide new insights into the evolution of the Red Planet and the history of volcanic activity there. NWA 7635 was compared with 11 other Martian meteorites, of a type called shergottites. Analysis of their chemical composition reveals the length of time they spent in space, how long they’ve been on Earth, their age, and their volcanic source. All 12 of them are from the same volcanic source.
Mars has much weaker gravity than Earth, so when something large enough slams into the Martian surface, pieces of rock are ejected into space. Some of these rocks eventually cross Earth’s path and are captured by gravity. Most burn up, but some make it to the surface of our planet. In the case of NWA 7635 and the other meteorites, they were ejected from Mars about 1 million years ago.
“We see that they came from a similar volcanic source,” Lapen said. “Given that they also have the same ejection time, we can conclude that these come from the same location on Mars.”
Taken together, the meteorites give us a snapshot of one location of the Martian surface. The other meteorites range from 327 million to 600 million years old. But NWA 7635 was formed 2.4 billion years ago. This means that its source was one of the longest lived volcanoes in our entire Solar System.
This false color X-ray of NWA 7635 shows the meteorite’s mineralogy mineral textures. O, olivine; P, plagioclase (maskelynite); C, clinopyroxene (augite). Chemical compositions: Fe (purple), Mg (green), Ca (blue), Ti (magenta), and S (yellow). Purple colors in the mesostasis represent Fe-rich augite. You’re welcome, mineral nerds. Image: Lapen et. al.
Volcanic activity on Mars is an important part of understanding the planet, and whether it ever harbored life. It’s possible that so-called super-volcanoes contributed to extinctions here on Earth. The same thing may have happened on Mars. Given the massive size of Olympus Mons, it could very well have been the Martian equivalent of a super-volcano.
The ESA’s Mars Express Orbiter sent back images of Olympus Mons that showed possible lava flows as recently as 2 million years ago. There are also lava flows on Mars that have a very small number of impact craters on them, indicating that they were formed recently. If that is the case, then it’s possible that Martian volcanoes will be visibly active again.
A colorized image of the surface of Mars taken by the Mars Reconnaissance Orbiter. The line of three volcanoes is the Tharsis Montes, with Olympus Mons to the northwest. Valles Marineris is to the east. Image: NASA/JPL-Caltech/ Arizona State University
Continuing volcanic activity on Mars is highly speculative, with different researchers arguing for and against it. The relatively crater-free, smooth surfaces of some lava features on Mars could be explained by erosion, or even glaciation. In any case, if there is another eruption on Mars, we would have to be extremely lucky for one of our orbiters to see it.
Using its HiRISE camera, the MRO has noted existence of tall networks of ridges on Mars that have diverse origins. Credit: NASA/JPL-Caltech/Univ. of Arizona
Mars has some impressive geological features across its cold, desiccated surface, many of which are similar to featured found here on Earth. By studying them, scientists are able to learn more about the natural history of the Red Planet, what kinds of meteorological phenomena are responsible for shaping it, and how similar our two planets are. A perfect of example of this are the polygon-ridge networks that have been observed on its surface.
One such network was recently discovered by the Mars Reconnaissance Orbiter (MRO) in the Medusae Fossae region, which straddles the planet’s equator. Measuring some 16 story’s high, this ridge network is similar to others that have been spotted on Mars. But according to a survey produced by researchers from NASA’s Jet Propulsion Laboratory, these ridges likely have different origins.
This survey, which was recently published in the journal Icarus, examined both the network found in the Medusae Fossae region and similar-looking networks in other regions of the Red Planet. These ridges (sometimes called boxwork rides), are essentially blade-like walls that look like multiple adjoining polygons (i.e. rectangles, pentagons, triangles, and similar shapes).
Shiprock, a ridge-feature in northwestern New Mexico that is 10 meters (30 feet) tall, which formed from lava filling an underground fracture that resisted erosion better than the material around it did. Credit: NASA
While similar-looking ridges can be found in many places on Mars, they do not appear to be formed by any single process. As Laura Kerber, of NASA’s Jet Propulsion Laboratory and the lead author of the survey report, explained in a NASA press release:
“Finding these ridges in the Medusae Fossae region set me on a quest to find all the types of polygonal ridges on Mars… Polygonal ridges can be formed in several different ways, and some of them are really key to understanding the history of early Mars. Many of these ridges are mineral veins, and mineral veins tell us that water was circulating underground.”
Such ridges have also been found on Earth, and appear to be the result of various processes as well. One of the most common involves lava flowing into preexisting fractures in the ground, which then survived when erosion stripped the surrounding material away. A good example of this is the Shiprock (shown above), a monadrock located in San Juan County, New Mexico.
Examples of polygon ridges on Mars include the feature known as “Garden City“, which was discovered by the Curiosity rover mission. Measuring just a few centimeters in height, these ridges appeared to be the result of mineral-laden groundwater moving through underground fissures, which led to standing mineral veins once the surrounding soil eroded away.
Mineral veins at the “Garden City” site, examined by NASA’s Curiosity Mars rover. Credit: NASA/JPL
At the other end of the scale, ridges that measure around 2 kilometers (over a mile) high have also been found. A good example of this is “Inca City“, a feature observed by the Mars Global Surveyor near Mars’ south pole. In this case, the feature is believed to be the result of underground faults (which were formed from impacts) filling with lava over time. Here too, erosion gradually stripped away the surrounding rock, exposing the standing lava rock.
In short, these features are evidence of underground water and volcanic activity on Mars. And by finding more examples of these polygon-ridges, scientists will be able to study the geological record of Mars more closely. Hence why Kerber is seeking help from the public through a citizen-science project called Planet Four: Ridges.
Established earlier this month on Zooniverse – a volunteer-powered research platform – this project has made images obtained by the MRO’s Context Camera (CTX) available to the public. Currently, this and other projects using data from CTX and HiRISE have drawn the participation of more than 150,000 volunteers from around the world.
By getting volunteers to sort through the CTX images for ridge formations, Kerber and her team hopes that previously-unidentified ones will be identified and that their relationship with other Martian features will be better understood.
Earth, seen from space, above the Pacific Ocean. Credit: NASA
One look at planet Earth on a map, or based on an image taken from space, ought to convey just how immense and important our oceans are. After all, they cover 72% of the planet’s surface, occupy a total volume of around 1.35 billion cubic kilometers (320 million cu mi), and are essential to life as we know it. And in their great depths, many mysteries still wait to be discovered.
Thanks to modern science and improvement exploration vehicles, one of the most obvious has been tackled – which is the mystery of where the deepest ocean in the world lies. This is none other than the Pacific Ocean, which averages approximately 4,280 meters (14,042 ft) in depth and contains the deepest known part of any ocean – the Mariana Trench.
Methodology:
Of course, determining the depth of an ocean is tricky business, and for obvious reasons. Ocean floors are extremely extensive, and vary widely in terms of elevation. Much like continental land masses, they have mountain ranges and trenches that throw off the curve. And in some cases, the trenches are much deeper than the average depth.
The view of the Pacific Ocean from the ISS. Credit: NASA
However, in terms of average depth, the Pacific Ocean is the deepest. Though calculations vary, it is estimated that the entire ocean floor averages about 4,280 meters (14,042 ft), which is over 500 m (1640 ft) deeper than the global average of 3,700 meters (12,100 ft). Part of the reason for this is due to the Marian Trench, which is significantly deeper!
Characteristics:
The Marian Trench is located in the western Pacific Ocean near the Mariana Islands, almost equally distant from both the Philippines and Japan. The trench is crescent shaped, and measures roughly 2,550 kilometers (1,580 mi) long with an average width of 69 kilometers (43 mi).
It reaches a maximum-known depth of 10,994 meters (36,070 ft) – with a margin of error of 40 metes (130 ft) – at a small slot-shaped valley in its floor known as the Challenger Deep, located at its southern end. Countries near the trench include Japan, Papua New Guinea, Indonesia and the Philippines.
The geological feature is the result of subduction that occurs at the boundary between two tectonic plates – the Filipino and the Pacific Plate. This results in what is known as the Izu-Bonin-Mariana subduction system, where the western edge of the Pacific Plate is subducted (pushed under) the smaller Mariana plate (part of the Filipino Plate).
Location of the Mariana Trench. Credit: Wikipedia Commons/Kmusser
The movement of the Pacific and Mariana Plates also led to the formation of the Mariana Islands, which are volcanic in nature. They formed as a result of flux melting – i.e. where water cools hot lava – due to the release of water that was trapped in the subducted portion of the Pacific Plate.
To put just how deep the Mariana Trench is into perspective, let’s consider comparing it to Mount Everest. If you placed Mt. Everest inside the Mariana Trench, there would still be over 2,000 meters (6562 ft) of water covering the mountain.
The water pressure in the Mariana Trench is also 15,750 psi, which is more than 1000 times greater than the standard atmospheric pressure at sea level. This means that if you could stand at the bottom of the Mariana Trench, the pressure could literally crush you!
Measurement:
Numerous measurements of the trench have been taken over the years using different methods. The first mission was the Challenger expedition, which took place between 1872 and 1876. Using the sounding technique, they measured the deepest point of Mariana Trench to 9,636 meters (31,614 ft).
The HMS Challenger, which conducted the Challenger II measurements of the Mariana Trench. Credit: Imperial War Museums.
This was followed by the HMS Challenger, which conducted the Challenger II survey in 1931. Here, surveyors relied on the more accurate technique of echo-sounding, and retrieved a deepest measurement of 10,900 meters (35,760 ft). This area came to be known as the Challenger Deep.
During the latter half of the 20th century, multiple missions would be conducted. In 1957, the Soviet vessel Vityaz obtained depth readings of 11,034 meters (36,201 ft) at a location named “the Mariana Hollow”. This was followed in 1962 by the US merchant vessel Spencer F. Baird, which recorded a maximum depth of 10,915 meters (35,810 ft) using precision depth gauges.
In 1984, the Japanese survey vessel Takuyo used a narrow, multi-beam echo sounder and reported a maximum depth of 10,924 meters (35,840 ft). In 1995, another Japanese vessel – the remotely operated vehicle KAIKO – reached the deepest area of the Mariana trench, thus establishing the deepest diving record of 10,911 meters (35,797 ft).
In 2009, the US research vessel Kilo Moana conducted the most accurate measurements of the Mariana Trench to date. This involved using sonar to map the Challenger Deep, which located a spot with a maximum depth of 10,971 meters (35,994 ft).
Rear view of the research vessel Kilo Moana. NOAA
Exploration:
Four missions have been made into the Mariana Trench. The first was the Trieste, a Swiss-designed, Italian-built, and US Navy-owned self-propelled submersible craft. On January 23rd, 1960, the craft and its two-man crew reached the bottom of the Trench, having reached a depth of 10,916 m (35,814 ft). This was followed by the unmanned Kaiko craft in 1996 and the autonomous craft Nereus in 2009.
The first three expeditions directly measured very similar depths of 10,902 to 10,916 m (35,768 to 35,814 ft). The fourth mission took place in 2012, where Canadian film director James Cameron mounted a mission using the submersible Deepsea Challenger. On March 26th, he reached the bottom of the Mariana Trench.
Several more missions have been planned as of February of 2012. These include Triton Submarines, a Florida-based company that designs and manufactures private submarines; and DOER Marine, a marine technology company based near San Francisco that plans to send a two or three-person sub to the seabed.
Beyond the coastlines, the world’s oceans are deep and unfathomable. Much of it remains unexplored and the life that scientists have found there is quite exotic (and may even provide insight into life on other worlds). Somehow, it seems appropriate that life in “inner space” would help us to understand life in “outer space”.
The "Global Tectonic and Volcanic Activity of the Last One Million Years" map. Credit: NASA/DTAM
For people who live on or near an active fault line – such as the San Andreas Fault in California, the Median Tectonic Line in Japan, or the Sunda Megathrust of southeast Asia – earthquakes are a regular part of life. Oftentimes, they can take the form of minor tremors that come and go without causing much damage.
But at other times, they are cataclysmic, causing widespread destruction and death tolls in the thousands or more. But what exactly is an earthquake? What geological forces lead to this destructive force? Where do they typically happen, and how many different types are there? And most importantly, how can we be better prepared for them?
Definition:
An earthquake is defined as a perceptible tremor in the surface of the Earth, which is caused by seismic waves resulting from the sudden release of energy in the Earth’s crust. Sometimes, they are detected because of the transfer of this energy to structures, causing noticeable shaking and noise. At other times, they can be violent enough to throw people and level entire cities.
Global earthquake epicenters, 1963–1998. Credit: NASA/DTAM
Generally, the term is used to describe any seismic event that generates seismic waves. An earthquake’s point of initial rupture is called its focus or hypocenter, while the point on the Earth directly above it (i.e. the most immediately-effected area) is called the epicenter.
Causes:
The structure of the Earth’s crust, which is divided into several “tectonic plates”, is responsible for most earthquakes. These plates are constantly in motion due to convection in the Earth’s semi-viscous upper mantle. Over time, these plates will separate and crash into each other, creating visible boundaries called faults.
When plates collide, they remain locked until enough pressure builds that one of them is forced under the other (a process known as subduction). This process occurs over the course of millions of years, and occasionally results in a serious release of energy, frictional heating and cracking along the fault lines (aka. an earthquake).
The energy waves that result are divided into two categories – surface waves and body waves. Surface waves are so-named because they are the energy that reaches the surface of the Earth, while body waves refer to the energy that remains within the planet’s interior.
Map of the Earth’s Tectonic Plates. Credit: msnucleus.org
It is estimated that only 10% or less of an earthquake’s total energy is radiated as seismic energy, while the rest is used to power the fracture growth or is converted into friction heat. However, what reaches the surface triggers all of the effects that we humans associate with earthquakes – i.e. tremors that vary in duration and intensity.
Occasionally, earthquakes can happen away from fault lines. These are due to some plate boundaries being located in regions of continental lithosphere, where deformation is spread out over a much larger area than the plate boundary. Under these conditions, earthquakes are related to strains developed within the broader zone of deformation.
Earthquakes within a plate (called “intraplate earthquakes”) can also happen as a result of internal stress fields, which are caused by interaction with neighboring plates, as well as sedimentary loading or unloading.
Aside from naturally occurring earthquakes (aka. tectonic earthquakes) that occur along tectonic plate lines (fault lines), there are also those that fall under the heading of “human-made earthquakes”. These are all the result of human activity, which is most often the result of nuclear testing.
Earthquakes can also be caused by human-made factors, such as nuclear testing. Credit: NNSA
This type of earthquake can been felt all from considerable distance after the detonation of a nuclear weapon. There is very little actual data that is readily available on this type of earthquake, but, compared to tectonic activity, it can be easily predicted and controlled.
Measurements:
Scientists measure earthquakes using seismometers, which measures sound waves through the Earth’s crust. There is also a method of measuring the intensity of an earthquake. It is known as the Richter Scale, which grades earthquakes from 1 to 10 based on their intensity.
Although there is no upper limit to the scale, most people set ten as the upper limit because no earthquakes equal to or greater than ten have been recorded. Scientist hypothesize that level 10 earthquakes were probably more common in prehistoric times, especially as the result of meteor impacts.
Effects of Earthquakes:
Earthquakes can happen on land or at sea, and can therefore trigger other natural disasters. In the case of those that take place on land, displacement of the ground is often the result, which can cause landslides or even volcanoes. When they take place at sea, the displacement of the seabed often results, causing a tsunami.
Map of earthquakes around the world in a seven day period. Credit: USGS / Google Maps / AJAX / SODA
Even though major earthquakes do not happen that often, they can cause substantial damage. In addition to the aforementioned natural disasters they can cause, earthquakes can also trigger fires when gas or electrical lines are damaged and floods when dams are destroyed.
Some of the most devastating earthquakes in history include the 1556 Shaanxi earthquake, which occurred on January 1556 in China. This quake resulted in widespread destruction of housing in the region – most of the housing being dwellings carved directly out of the silt stone mountain – and led to over 830,000 deaths.
The 1976 Tangshan earthquake, which took place in north-eastern China, was the deadliest of the 20th century, leading to he deaths of between 240,000 and 655,000 people. The 1960 Chilean earthquake is the largest earthquake that has been measured on a seismograph, reaching 9.5 magnitude on May 22nd, 1960.
And then there was the 2004 Indian Ocean earthquake, a seismic event that also triggered a massive tsunami that caused devastation throughout southeast Asia. This quake reached 9.1 – 9.3 on the Richter Scale, struck coastal communities with waves measuring up to 30 meters (100 ft) high, and caused the deaths of 230,000 people in 14 countries.
A village near the coast of Sumatra that was devastated by the 2004 Tsunami. Credit: Wikipedia Commons/US Navy
Warning Systems:
More than 3 million earthquakes occur each year, which works out to about 8,000 earthquakes each day. Most of these occur in specific regions, mainly because they usually happen along the borders of tectonic plates. Despite being difficult to predict (except where human agency is the cause) some early warning methods have been devised.
For instance, using seismological data obtained in well-understood fault regions, earthquakes can be reasonably predicted weeks or months in advance. Regional notifications are also used whenever earthquakes are in progress, but before the shocks have struck, allowing people time to seek shelter in time.
Much like volcanoes, tornadoes, and debris flows, earthquakes are a force of nature that is not to be taken lightly. While they are a regular feature of our planet’s geological activity, they have had a considerable impact on human societies. And just like the eruption that buried Pompeii or the Great Flood, they are remembered long after they strike!
Landslides constitute one of the most destructive geological hazards in the world today. One of the main reasons for this is because of the high speeds that slides can reach, up to 160 km/hour (100 mph). Another is the fact that these slides can carry quite a bit of debris with them that serve to amplify their destructive force.
Taken together, this is what is known as a Debris Flow, a natural hazard that can take place in many parts of the world. A single flow is capable of burying entire towns and communities, covering roads, causing death and injury, destroying property and bringing all transportation to a halt. So how do we deal with them?
Definition:
A Debris Flow is basically a fast-moving landslide made up of liquefied, unconsolidated, and saturated mass that resembles flowing concrete. In this respect, they are not dissimilar from avalanches, where unconsolidated ice and snow cascades down the surface of a mountain, carrying trees and rocks with it.
Images of a Debris Flow Chute and Deposit, taken by the Arizona Geological Survey (AZGS). Credit: azgs.com
A common misconception is to confuse debris flows with landslides or mudflows. In truth, they differ in that landslides are made up of a coherent block of material that slides over surfaces. Debris flows, by contrast, are made up of “loose” particles that move independently within the flow.
Similarly, mud flows are composed of mud and water, whereas debris flows are made up larger particles. All told, it has been estimated that at least 50% of the particles contained within a debris flow are made-up of sand-sized or larger particles (i.e. rocks, trees, etc).
Types of Flows:
There are two types of debris flows, known as Lahar and Jökulhlaup. The word Lahar is Indonesian in origin and has to do with flows that are related to volcanic activity. A variety of factors may trigger a lahar, including melting of glacial ice due to volcanic activity, intense rainfall on loose pyroclastic material, or the outbursting of a lake that was previously dammed by pyroclastic or glacial material.
Jökulhlaup is an Icelandic word which describes flows that originated from a glacial outburst flood. In Iceland, many such floods are triggered by sub-glacial volcanic eruptions, since Iceland sits atop the Mid-Atlantic Ridge. Elsewhere, a more common cause of jökulhlaups is the breaching of ice-dammed or moraine-dammed lakes.
Debris flow channel in Ladakh, near the northwestern Indian Himalaya, produced in the storms of August 2010. Credit: Wikipedia Commons/DanHobley
Such breaching events are often caused by the sudden calving of glacier ice into a lake, which then causes a displacement wave to breach a moraine or ice dam. Downvalley of the breach point, a jökulhlaup may increase greatly in size by picking up sediment and water from the valley through which it travels.
Causes of Flows:
Debris flows can be triggered in a number of ways. Typically, they result from sudden rainfall, where water begins to wash material from a slope, or when water removed material from a freshly burned stretch of land. A rapid snowmelt can also be a cause, where newly-melted snow water is channeled over a steep valley filled with debris that is loose enough to be mobilized.
In either case, the rapidly moving water cascades down the slopes and into the canyons and valleys below, picking up speed and debris as it descends the valley walls. In the valley itself, months’ worth of built-up soil and rocks can be picked up and then begin to move with the water.
As the system gradually picks up speed, a feedback loop ensues, where the faster the water flows, the more it can pick up. In time, this wall begins to resemble concrete in appearance but can move so rapidly that it can pluck boulders from the floors of the canyons and hurl them along the path of the flow. It’s the speed and enormity of these carried particulates that makes a debris flow so dangerous.
Deforestation (like this clearcut in Sumatra, Indonesia) can result in debris flows. Credit: worldwildlife.org
Another major cause of debris flows is the erosion of steams and riverbanks. As flowing water gradually causes the banks to collapse, the erosion can cut into thick deposits of saturated materials stacked up against the valley walls. This erosion removes support from the base of the slope and can trigger a sudden flow of debris.
In some cases, debris flows originate from older landslides. These can take the form of unstable masses perched atop a steep slope. After being lubricated by a flow of water over the top of the old landslide, the slide material or erosion at the base can remove support and trigger a flow.
Some debris flows occur as a result of wildfires or deforestation, where vegetation is burned or stripped from a steep slope. Prior to this, the vegetation’s roots anchored the soil and removed absorbed water. The loss of this support leads to the accumulation of moisture which can result in structural failure, followed by a flow.
Sarychev volcano, (located in Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA
A volcanic eruption can flash melt large amounts of snow and ice on the flanks of a volcano. This sudden rush of water can pick up ash and pyroclastic debris as it flows down the steep volcano and carry them rapidly downstream for great distances.
In the 1877 eruption of Cotopaxi Volcano in Ecuador, debris flows traveled over 300 kilometers down a valley at an average speed of about 27 kilometers per hour. Debris flows are one of the deadly “surprise attacks” of volcanoes.
Prevention Methods:
Many methods have been employed for stopping or diverting debris flows in the past. A popular method is to construct debris basins, which are designed to “catch” a flow in a depressed and walled area. These are specifically intended to protect soil and water sources from contamination and prevent downstream damage.
Some basins are constructed with special overflow ducts and screens, which allow the water to trickle out from the flow while keeping the debris in place, while also allowing for more room for larger objects. However, such basins are expensive, and require considerable labor to build and maintain; hence why they are considered an option of last resort.
Aerial view of the destruction caused by a debris-flow in the Venezuelan town of Caraballeda. Credit: US Geological Survey
Currently, there is no way to monitor for the possibility of debris flow, since they can occur very rapidly and are often dependent on cycles in the weather that can be unpredictable. However, early warning systems are being developed for use in areas where debris flow risk is especially high.
One method involves early detection, where sensitive seismographs detect debris flows that have already started moving and alert local communities. Another way is to study weather patterns using radar imaging to make precipitation estimates – using rainfall intensity and duration values to establish a threshold of when and where a flows might occur.
In addition, replanting forests on hillsides to anchor the soil, as well as monitoring hilly areas that have recently suffered from wildfires is a good preventative measure. Identifying areas where debris flows have happened in the past, or where the proper conditions are present, is also a viable means of developing a debris flow mitigation plan.
Volcanoes are an impressive force of nature. Physically, they dominate the landscape, and have an active role in shaping our planet’s geography. When they are actively erupting, they are an extremely dangerous and destructive force. But when they are passive, the soil they enrich can become very fertile, leading to settlements and cities being built nearby.
Such is the nature of volcanoes, and is the reason why we distinguish between those that are “active” and those that are “dormant”. But what exactly is the differences between the two, and how do geologists tell? This is actually a complicated question, because there’s no way to know for sure if a volcano is all done erupting, or if it’s going to become active again.
Put simply, the most popular way for classifying volcanoes comes down to the frequency of their eruption. Those that erupt regularly are called active, while those that have erupted in historical times but are now quiet are called dormant (or inactive). But in the end, knowing the difference all comes down to timing!
Sarychev volcano, (located in Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA
Active Volcano:
Currently, there is no consensus among volcanologists about what constitutes “active”. Volcanoes – like all geological features – can have very long lifespans, varying between months to even millions of years. In the past few thousand years, many of Earth’s volcanoes have erupted many times over, but currently show no signs of impending eruption.
As such, the term “active” can mean only active in terms of human lifespans, which are entirely different from the lifespans of volcanoes. Hence why scientists often consider a volcano to be active only if it is showing signs of unrest (i.e. unusual earthquake activity or significant new gas emissions) that mean it is about to erupt.
Aleutian island #volcano letting off a little steam after the new year on Jan 2, 2016. #YearInSpace. Credit: NASA/Scott Kelly/@StationCDRKelly
By this definition, those volcanoes that have erupted in the course of human history (which includes more than 500 volcanoes) are defined as active. However, this too is problematic, since this varies from region to region – with some areas cataloging volcanoes for thousands of years, while others only have records for the past few centuries.
As such, an “active volcano” can be best described as one that’s currently in a state of regular eruptions. Maybe it’s going off right now, or had an event in the last few decades, or geologists expect it to erupt again very soon. In short, if its spewing fire or likely to again in the near future, then it’s active!
Dormant Volcano:
Meanwhile, a dormant volcano is used to refer to those that are capable of erupting, and will probably erupt again in the future, but hasn’t had an eruption for a very long time. Here too, definitions become complicated since it is difficult to distinguish between a volcano that is simply not active at present, and one that will remain inactive.
Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time. For instance, the volcanoes of Yellowstone, Toba, and Vesuvius were all thought to be extinct before their historic and devastating eruptions.
The area around Mount Vesuvius, which erupted in 79 CE, is now densely populated. Credit: Wikipedia Commons/Jeffmatt
The same is true of the Fourpeaked Mountain eruption in Alaska in 2006. Prior to this, the volcano was thought to be extinct since it had not erupted for over 10,000 years. Compare that to Mount Grímsvötn in south-east Iceland, which erupted three times in the past 12 years (in 2011, 2008 and 2004, respectively).
And so a dormant volcano is actually part of the active volcano classification, it’s just that it’s not currently erupting.
Extinct Volcano:
Geologists also employ the category of extinct volcano to refer to volcanoes that have become cut off from their magma supply. There are many examples of extinct volcanoes around the world, many of which are found in the Hawaiian-Emperor Seamount Chain in the Pacific Ocean, or stand individually in some areas.
For example, the Shiprock volcano, which stands in Navajo Nation territory in New Mexico, is an example of a solitary extinct volcano. Edinburgh Castle, located just outside the capitol of Edinburgh, Scotland, is famously located atop an extinct volcano.
Aerial photograph of the Shiprock extinct volcano. Credit: Wikipedia Commons
But of course, determining if a volcano is truly extinct is often difficult, since some volcanoes can have eruptive lifespans that measure into the millions of years. As such, some volcanologists refer to extinct volcanoes as inactive, and some volcanoes once thought to be extinct are now referred to as dormant.
In short, knowing if a volcano is active, dormant, or extinct is complicated and all comes down to timing. And when it comes to geological features, timing is quite difficult for us mere mortals. Individuals and generations have limited life spans, nations rise and fall, and even entire civilization sometimes bite the dust.
But volcanic formations? They can endure for millions of years! Knowing if there still life in them requires hard work, good record-keeping, and (above all) immense patience.
Future missions to Mars and other locations in the Solar System may depend heavily on the skills of planetary geologists. Credit: NASA Ames Research Center
In the coming decades, the world’s largest space agencies all have some rather big plans. Between NASA, the European Space Agency (ESA), Roscosmos, the Indian Space Research Organisation (ISRO), or the China National Space Administration (CNSA), there are plans to return to the Moon, crewed missions to Mars, and crewed missions to Near-Earth Objects (NEOs).
In all cases, geological studies are going to be a major aspect of the mission. For this reason, the ESA recently unveiled a new training program known as the Pangaea course, a study program which focuses on identifying planetary geological features. This program showcases just how important planetary geologists will be to future missions.
Pangaea takes its name from the super-continent that that existed during the late Paleozoic and early Mesozoic eras (300 to 175 million years ago). Due to convection in Earth’s mantle, this continent eventually broke up, giving rise to the seven continents that we are familiar with today.
The super-continent Pangea during the Permian period (300 – 250 million years ago). Credit: NAU Geology/Ron Blakey
Francesco Sauro – a field geologist, explorer and the designer of the course – explained the purpose of Pangaea in an ESA press release:
“This Pangaea course – named after the ancient supercontinent – will help astronauts to find interesting rock samples as well as to assess the most likely places to find traces of life on other planets. We created a course that enables astronauts on future missions to other planetary bodies to spot the best areas for exploration and the most scientifically interesting rocks to take samples for further analysis by the scientists back on Earth.”
This first part of the course will take place this week, where astronaut trainer Matthias Maurer and astronauts Luca Parmitano and Pedro Duque will be learning from a panel of planetary geology experts. These lessons will include how to recognize certain types of rock, how to draw landscapes, and the exploration of a canyon that has sedimentary features similar to the ones observed in the Murray Buttes region, which was recently imaged by the Curiosity rover.
The geology panel will include such luminaries as Matteo Messironi (a geologist working on the Rosetta and ExoMars missions), Harald Hiesinger (an expert in lunar geology), Anna Maria Fioretti (a meteorite expert), and Nicolas Mangold (a Mars expert currently working with NASA’s Curiosity team).
Rock samples on display at ESA’s Pangaea training course, which is intended to help astronauts in identify planetary geological features for future missions to the Moon, Mars and asteroids. Credit: ESA/L. Bessone
Once this phase of the course is complete, a series of field trips will follow to locations that were chosen because their geological features resemble those of other planets. This will include the town of Bressanone in northeastern Italy, which lies a few kilometers outside of the Brenner Pass (the part of the Alps that lies between Italy and Austria).
This past summer, the latest program involved a team of six international astronauts spending two weeks in a cave network in Sardinia, Italy. In this environment, 800-meters (2625 ft) beneath the surface, the team carried out a series of research and exploration activities designed to recreate aspects of a space expedition.
As the teams explore the caves of Sardinia, they encountered caverns, underground lakes and examples of strange microscopic life – all things they could encounter in extra-terrestrial environments. While doing this, they also get the change to test out new technologies and methods for research and experiments.
Sedimentary outcroppings in the Bressanoe region (left), compared to sedimentary deposits in the Murray Buttes region on Mars (right). Credit: ESA/I. Drozdovsky (left); NASA (right)
In a way that is similar to expeditions aboard the ISS, the program was designed to teach an international team of astronauts how to address the challenges of living and working in confined spaces. These include limited privacy, less equipment for hygiene and comfort, difficult conditions, variable temperatures and humidity, and extremely difficult emergency evacuation procedures.
Above all, the program attempts to foster teamwork, communication skills, decision-making, problem-solving, and leadership. This program is now an integral part of the ESA’s astronaut training and is conducted once a year. And as project leader Loredana Bessone explained, the Pangaea course fits with the aims of the CAVES program quite well.
“Pangaea complements our CAVES underground training,” she said. “CAVES focuses on team behaviour and operational aspects of a space mission, whereas Pangaea focuses on developing knowledge and skills for planetary geology and astrobiology.”
From all of these efforts, it is clear that the ESA, NASA and other space agencies want to make sure that future generations of astronauts are trained to conduct field geology and will be able to identify targets for scientific research. But of course, understanding the importance planetary geology in space exploration is not exactly a new phenomenon.
The six-member CAVES team in Sardinia, Italy, observing an underground pool. Credit: ESA/V. Crobu
In fact, the study of planetary geology is rooted in the Apollo era, when it became a field separate from other fields of geological research. And geology experts played a very pivotal role when it came to selecting the landing sites of the Apollo missions. As Emily Lakdawalla, the Senior Editor of The Planetary Society (and a geologist herself), told Universe Today in a phone interview:
“The Apollo astronauts received training in field geology before they went to the Moon. Jim Head at Brown University, who was my advisor, was one person who provided that training. Before there were missions, the Lunar Orbiter program returned photos that geologists used to map the surface of the Moon and find good landing sites.”
This tradition is being carried on today with instruments like the Mars Global Surveyor. Before the Spirit and Opportunity rovers were deployed to the Martian surface, NASA scientists studied images taken by this orbiter to determine which potential landing sites would prove to be the valuable for conducting research.
And thanks to the experience gained by the Apollo missions and improvements made in both technology and instrumentation, the process has become much more sophisticated. Compared to the Apollo-era, today’s NASA mission planners have much more detailed information to go on.
Moon rocks from the Apollo 11 mission. Credit: NASA
“These days, the orbiter photos have such high resolutions that its just like having aerial photographs, which is something Earth geologists have always used as a tool to scope out an area before going to study it,” Lakdawalla said. “With these photos, we can map out an area in detail before we send a rover, and determine where the most high-value samples will be.”
Looking ahead, everything that’s learned from sending astronauts to the Moon – and from the study of the lunar rocks they brought back – is going to play a vital role when it comes time to explore Mars, go back to the Moon, and investigate NEOs. As Lakdawalla explained, in each case, the purpose of the geological studies will be a bit different.
“The goal in obtaining samples from the Moon was about understanding the chronology of the Moon. The timescale we have developed for the Moon are anchored in the Apollo samples. But we think that the samples have been sampling one major impact – the Imbrium impact. The next Moon samples will attempt to sample other time periods so we can determine if our time scales are correct.”
“On Mars, the questions is, ‘what are the history of water on Mars’. You try to find rocks from orbit that will answer that questions – rocks that have either been altered by water or formed in water. And that is how you select your landing zone.”
And with future missions to NEOs, astronauts will be tasked with examining geological samples which date back to the formation of the Solar System. From this, we are likely to get a better understanding of how our Solar System formed and evolved over the many billion years it has existed.
Clearly, it is a good time to be a geologist, as their expertise will be called upon for future missions to space. Hope they like tang!
The 2006 Cleveland Volcano Eruption viewed from space. Credit: NASA
Volcanoes come in many shapes and sizes, ranging from common cinder cone volcanoes that build up from repeated eruptions and lava domes that pile up over volcanic vents to broad shield volcanoes and composite volcanoes. Though they differ in terms of structure and appearance, they all share two things. On the one hand, they are all awesome forces of nature that both terrify and inspire.
On the other, all volcanic activity comes down to the same basic principle. In essence, all eruptions are the result of magma from beneath the Earth being pushed up to the surface where it erupts as lava, ash and rock. But what mechanisms drive this process? What is it exactly that makes molten rock rise from the Earth’s interior and explode onto the landscape?
To understand how volcanoes erupt, one first needs to consider the structure of the Earth. At the very top is the lithosphere, the outermost layers of the Earth that consists of the upper mantle and crust. The crust makes up a tiny volume of the Earth, ranging from 10 km in thickness on the ocean floor to a maximum of 100 km in mountainous regions. It is cold and rigid, and composed primarily of silicate rock.
The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
Beneath the crust, the Earth’s mantle is divided into sections of varying thickness based on their seismology. These consist of the upper mantle, which extends from a depth of 7 – 35 km (4.3 to 21.7 mi)) to 410 km (250 mi); the transition zone, which ranges from 410–660 km (250–410 mi); the lower mantle, which ranges from 660–2,891 km (410–1,796 mi); and the core–mantle boundary, which is ~200 km (120 mi) thick on average.
In the mantle region, conditions change drastically from the crust. Pressures increase considerably and temperatures can reach up to 1000 °C, which makes the rock viscous enough that it behaves like a liquid. In short, it experiences elastically on time scales of thousands of years or greater. This viscous, molten rock collects into vast chambers beneath the Earth’s crust.
Since this magma is less dense than the surrounding rock, it ” floats” up to the surface, seeking out cracks and weaknesses in the mantle. When it finally reaches the surface, it explodes from the summit of a volcano. When it’s beneath the surface, the molten rock is called magma. When it reaches the surface, it erupts as lava, ash and volcanic rocks.
The Earth’s Tectonic Plates. Credit: msnucleus.org
With each eruption, rocks, lava and ash build up around the volcanic vent. The nature of the eruption depends on the viscosity of the magma. When the lava flows easily, it can travel far and create wide shield volcanoes. When the lava is very thick, it creates a more familiar cone volcano shape (aka. a cinder cone volcano). When the lava is extremely thick, it can build up in the volcano and explode (lava domes).
Another mechanism that drives volcanism is the motion the crust undergoes. To break it down, the lithosphere is divided into several plates, which are constantly in motion atop the mantle. Sometimes the plates collide, pull apart, or slide alongside each other; resulting in convergent boundaries, divergent boundaries, and transform boundaries. This activity is what drives geological activity, which includes earthquakes and volcanoes.
In the case of the former, subduction zones are often the result, where the heavier plate slips under the lighter plate – forming a deep trench. This subduction changes the dense mantle into buoyant magma, which rises through the crust to the Earth’s surface. Over millions of years, this rising magma creates a series of active volcanoes known as a volcanic arc.
Cross-section of a volcano. Credit: 3dgeography.co.uk
In short, volcanoes are driven by pressure and heat in the mantle, as well as tectonic activity that leads to volcanic eruptions and geological renewal. The prevalence of volcanic eruptions in certain regions of the world – such as the Pacific Ring of Fire – also has a profound impact on the local climate and geography. For example, such regions are generally mountainous, have rich soil, and periodically experience the formation of new landmasses.
Mt. Chimborazo, located in Equator, is technically the highest point on Earth. Sorry, Everest! Credit: gerdbreitenbach.de
Whenever the question is asked, what is the highest point on planet Earth?, people naturally assume that the answer is Mt. Everest. In fact, so embedded is the notion that Mt. Everest is the highest point on the world that most people wouldn’t even think twice before answering. And even when we talk of other huge mountains in the Solar System (like Mars’ Olympus Mons), we invariably compare them to Mt. Everest.
But in truth, Everest does not hold the record for being the highest point on Earth. Due to the nature of our planet – which is not shaped like a perfect sphere but an oblate spheroid (i.e. a sphere that bulges at the center) – points that are located along the equator are farther away than those located at the poles. When you factor this in, Everest and the Himalayas find themselves falling a bit short!
Earth as a Sphere:
The understanding that Earth is spherical is believed to have emerged during the 6th century BCE in ancient Greece. While Pythagoras is generally credited with this theory, it is equally likely that it emerged on its own as a result of travel between Greek settlements – where sailors noticed changes in what stars were visible at night based on differences in latitudes.
Planet Earth, as seen from space above the Western Hemisphere. Credit: Reuters
By the 3rd century BCE, the idea of a spherical Earth began to become articulated as a scientific matter. By measuring the angle cast by shadows in different geographical locations, Eratosthenes – a Greek astronomer from Hellenistic Libya (276–194 BCE) – was able to estimate Earth’s circumference within a 5% – 15% margin of error. With the rise of the Roman Empire and their adoption of Hellenistic astronomy, the view of a spherical Earth became widespread throughout the Mediterranean and Europe.
This knowledge was preserved thanks to the monastic tradition and Scholasticism during the Middle Ages. By the Renaissance and the Scientific Revolution (mid 16th – late 18th centuries), the geological and heliocentric views of Earth became accepted as well. With the advent of modern astronomy, precise methods of measurement, and the ability to view Earth from space, our models of its true shape and dimensions have come to be refined considerably.
Modern Models of the Earth:
To clarify matters a little, the Earth is neither a perfect sphere, nor is it flat. Sorry Galileo, and sorry Flat-Earthers (not sorry!), but it’s true. As already noted, it is an oblate spheroid, which is a result of the rotation of the Earth. Basically, its spin results in a flattening at the poles and a bulging at its equatorial. This is true for many bodies in the Solar System (such as Jupiter and Saturn) and even rapidly-spinning stars like Altair.
Data from the Earth2014 global relief model, with distances from the geocenter represented in color. Credit: Geodesy2000
Based on some of the latest measurements, it is estimated that Earth has a polar radius (i.e. from the middle of Earth to the poles) of 6,356.8 km, whereas its equatorial radius (from the center to the equator) is 6,378.1 km. In short, objects located along the equator are 22 km further away from the center of the Earth (geocenter) than objects located at the poles.
Naturally, there are some deviations in the local topography where objects located away from the equator are closer or father away from the center of the Earth than others in the same region. The most notable exceptions are the Mariana Trench – the deepest place on Earth, at 10,911 m (35,797 ft) below local sea level – and Mt. Everest, which is 8,848 meters (29,029 ft) above local sea level. However, these two geological features represent a very minor variation when compared to Earth’s overall shape – 0.17% and 0.14% respectively.
Highest Point on Earth:
To be fair, Mt. Everest is one of the highest points on Earth, with its peak ascending to an altitude of 8,848 meters (29,029 ft) above sea level. However, due to its location within the Himalayan Mountain Chain in Nepal, some 27° and 59 minutes north of the equator, it is actually lower than mountains located in Ecuador.
It is here, where the land is dominated by the Andes mountain chain, that the highest point on planet Earth is located. Known as Mt. Chiborazo, the peak of this mountain reaches an attitude of 6,263.47 meters (20,549.54 ft) above sea level. But because it is located just 1° and 28 minutes south of the equator (at the highest point of the planet’s bulge), it receives a natural boost of about 21 km.
Mount Everest, imaged from Kalapatthar. Credit: Pavel Novak
In terms of how far they are from the geocenter, Everest lies at a distance of 6,382.3 kilometers (3,965.8 miles) from the center of the Earth while Chimborazo reaches to a distance of 6,384.4 kilometers (3,967.1 miles). That’s a difference of about 2.1 km (1.3 miles), which may not seem like much. But if we’re talking about rankings and titles, it pays to be specific.
Naturally, there are those who would stress that Mt. Everest is still the tallest mountain, measured from base to peak. Unfortunately, here too, they would be incorrect. That prize goes to Mauna Kea, a dormant volcano located on the island of Hawaii. Measuring 10,206 meters (33,484 ft) from base to summit, it is the highest mountain in the world. However, since its base is several thousand meters below seat level, we only see the top 4,207 m (13,802 ft) of it.
But if one were to say that Everest was tallest mountain based on its altitude, they would be correct. In terms of its summit’s elevation above sea level, Everest is ranked as being as the tallest mountain in the world. And when it comes to the sheer difficulty of ascending it, Everest will always be ranked no. 1, both in the records books and in the hearts of climbers everywhere!
An artist's impression of the ancient Martian ocean. When two meteors slammed into Mars 3.4 billion years ago, they triggered massive, 400 ft. tsunamis that reshaped the coastline. Image: ESO/M. Kornmesser, via N. Risinger
About 3.4 billion years ago, (according to a new study) when the Late Heavy Bombardment had ended, and the first cells resembling prokaryotes were appearing on Earth, two enormous meteoroids slammed into the ancient, frigid ocean on Mars. These impacts generated massive 400 ft. high tsunamis that reshaped the shoreline of the Martian ocean, leaving behind fields of sediments and boulders.
It was long thought that ancient Mars had oceans. Sedimentary deposits discovered in the Martian north by radar in 2012 helped make the case for Martian oceans. 3.4 billion years ago, this ocean covered most of the Northern Martian lowlands. It’s thought that the ocean itself was fed by catastrophic flooding, perhaps fuelled by geothermal activity on Mars at the time.
These catastrophic tsunamis would have dwarfed most Earthly disasters. Waves 120 meters high would have swamped landmarks like the Statue of Liberty (93 m. high), and caused enormous destruction along the Martian coastline. If the research behind this new study stands up to scrutiny, then it will help prove the existence of the ancient Martian ocean.
The blue area in the above image is thought to be the location of a primordial ocean Mars. Image: NASA/JPL-Caltech/GSFC – Public Domain
The Martian surface shows the remains of an ancient ocean. In some areas, radar data shows a layer of water-borne sediment on top of a layer of volcanic rock. There’s also evidence of a shoreline, described by some scientists as being like a bathtub ring. The problems is, the shoreline can’t be seen everywhere it should be.
The tsunami hypothesis helps explain this missing shoreline.
According to the new study, led by Alexis Rodriguez, a Mars researcher at the Planetary Science Institute in Tucson Arizona, the tsunamis would have wiped away portions of the coastline, and left behind fields of sediment and boulders, and large backwash channels cut into the Martian surface.
The study is focussed on a specific region on Mars where a highland feature called Arabia Terra abuts the Chryse Planitia lowlands. This area was part of the shoreline of the Martian ocean. In that area, the team behind the study identified two separate geological formations that they say were created by two separate tsunami events.
The top image shows the shoreline of the ancient Martian shoreline at two separate times. The bottom images show debris left behind by the two tsunamis. Image: Alexis Rodriguez.
The first formation, and older of the two, looks every bit like a disturbed shoreline. An enormous wave washed over the beach, and in its wake deposited boulders over 10 meters across. Then, as the water drained back down into the ocean, it cut large backwash channels through its debris and boulder field.
A sequence of zoomed in images of the Martian surface in the study. (A) shows distances and elevations of backwash channels. (B) shows some of the channel-scoured, north-sloping highland mesas in blue. (C) shows the channelled surface, and (D) shows them in closer detail. Finally, (E) is zoomed in to show boulders as much as 10 m. in diameter. (Yellow bars are 10m.) Image: A,B:MOLA Science Team, MSS, JPL, NASA. C,D,E: NASA/JPL/University of Arizona
Then, some time passed. Millions of years, probably, until the second meteor hit, triggering another enormous tsunami. But this one behaved a little differently.
Conditions on Mars had changed by then, with temperatures dropping, and glaciers marching across the landscape, gouging out deep valleys on the surface of Mars. When the second tsunami hit the shore, its effect was different.
This time, the tsunami was more like an icy slurry, according to the team. Because of the cold temperatures, the icy water froze in place in some areas, before it could wash back into the ocean. The result? Deposits of frozen debris formed in dense lobes on the surface.
This long lobe of dark material on the surface of Mars was left behind when a tsunami of icy flush washed over the Martian coastline, freezing in place before it could wash back into the sea. Image: Alexis Rodriquez
But according to Rodriguez, this is just a snapshot of a process that likely occurred multiple times in the history of Mars. Successive meteors could have caused successive mega-tsunamis that would have repeatedly wiped away evidence of a shoreline. This could have happened as often as every 3 million years.
This study isn’t the knockout blow that proves the existence of a Martian ocean in ancient times. But it is certainly intriguing, and is a reasonable hypothesis that explains missing shorelines.
Rodriguez intends to keep looking for other evidence of tsunamis on the Martian surface. If he finds more, it will help make the case for the meteor-tsunami explanation.
Rodriguez will also be visiting places on Earth that are analogues for the Martian surface of ancient times. This summer he plans on visiting high-altitude, cold, alpine lakes in Tibet, where he hopes to learn something about the processes and geological formations involved.
Even better would be a mission to Mars, to sample the area where the tsunamis came ashore. A group of small craters near the shore that were drenched by the tsunamis is of particular interest to Rodriguez and his team. Martian ocean water could have been trapped there for millions of years. This site could provide evidence about the briny nature of the ancient ocean on Mars, and possibly tell us something about the evolution of life there.
