Tag Archives: volcanoes

The main types of mountains — Earth’s ups and downs

Mountains have always played a central role in human culture, but we’ve only recently come to understand how they form and develop. To this day, these magnificent landforms still hold many secrets. There are several ways to analyze and classify mountains depending on your scientific discipline. Here, we’ll describe some of the more common classifications of mountains in detail.

Aerial view of Mount Everest from the south. The Himalayas are fold mountains. Image credits: airline company Drukair in Bhutan.

The Types of Mountains

Generally, mountains be classified as: fold mountains, block mountains, dome mountains, and volcanic mountains. Plateau mountains, uplifted passive margins, and hotspot mountains are also sometimes considered.

  • Fold mountains — the most common type, they form when two or more tectonic plates collide.
  • Block mountains (or fault-block) — formed through geological processes pushing some rocks up and others down.
  • Dome mountains — formed as a result of hot magma pushing beneath the crust.
  • Volcanic mountains — also known by a simpler name: volcanoes.
  • Other types of mountains sometimes included in classifications are plateau mountains, uplifted passive margins, and hotspot mountains.

Fold mountains

The Rocky Mountains are a great example of fold mountains. Image credits: National Park Service Digital Image Archives.

Fold mountains are the most common and most massive types of mountains (on Earth, at least). Fold mountain chains can spread over thousands of kilometers — we’re talking about the Himalayas, the Alps, the Rockies, the Andes — all the big boys. They’re also relatively young (another reason they’re so tall, as they haven’t been thoroughly eroded), but that’s “young” in geological terms — still tens of millions of years.

In order to understand how fold mountains form and develop, we have to think about plate tectonics. The Earth’s lithosphere is split into rigid plates which move independently of one another. There are seven major tectonic plates and several smaller ones all across the world.

When two plates collide, several things can happen. For instance, if one plate is denser than the other (oceanic plates are typically denser because of the type of rocks that make up the plate), a process called subduction will start: the heavier one will slowly glide beneath the lighter one. If they have relatively similar densities, then they will start to crumple up, driving movement upwards. Essentially, the tectonic plates are pushed, and since neither can slide beneath the other, they build up geological folds. To get a better idea of what this looks like, try to push two pieces of papers towards each other: some parts will rise up, representing the process of mountain formation.

Sometimes, the folding happens inside the continent and is associated with faulting. This is a representation of that process in northern Montana, USA, and Southern Alberta, Canada. Image credits: Greg Beaumont, National Park Service.

This process is called orogeny (giving birth to mountains) and it generally takes millions of years for it to complete. Many of today’s fold mountains are still developing as the tectonic process unfolds. The process doesn’t occur on tectonic edges — sometimes the mountain-generating fold process can take place well inside a tectonic plate.

Block mountains (or fault-block)

While the previous category was all about folds, this one is all about faults: geological faults, that is.

Depiction of the block-faulting process. Image credits: U.S. Geological Survey.

Let’s revisit the previous idea for a moment. Let’s say that while under pressure, some parts of a tectonic plate start to fold. As the pressure grows and grows, at one point the rock will simply break. Faults are those breaks: they’re the planar fractures or discontinuities in volumes of rock. Their size can vary tremendously, from a few centimeters to mountain-sized.

Basically, when big blocks of rock are broken through faulting, some of them can get pushed up or down, thus resulting in block mountains. Higher blocks are called horsts and troughs are called grabensTheir size can also be impressive, though they’re generally not as big as fold mountains because the process which generates them takes place on a smaller scale and involves less pressure. Still, the Sierra Nevada mountains (an example of block mountains), feature a block 650 km long and 80 km wide. Another good example is the Rhine Valley and the Vosges mountain in Europe. Rift valleys can also generate block mountains, as is the case in the Eastern African Rift.

Mount Alice and Temple Crag in the Sierra Nevada. Image credits: Miguel.v

It can be quite difficult to identify a block mountain without knowing its underlying geology but generally, they tend to have a steep side and a slowly sloping side.

Volcanic mountains

Annotated view includes Ushkovsky, Tolbachik, Bezymianny, Zimina, and Udina stratovolcanoes of Kamchatka, Russia. Image taken aboard the ISS in 2013.

Everyone knows something about volcanoes, though we rarely think about them as mountains (and truth be told, they aren’t always mountains).

Volcanic mountains are created when magma deep beneath the surface starts to rise up. At one point, it erupts in the form of lava and then cools down, solidifying and piling on to create a mountain. Mount Fuji in Japan and Mount Rainier are classic examples of volcanic mountains — with Mount Rainier being one of the most dangerous volcanoes in the world. However, it’s not necessary for the volcano to be active to be a volcanic mountain.

The summit of Mauna Kea. Image credits: Pixabay.

Several types of volcanoes can generate mountains, with Stratovolcanoes typically creating the biggest ones. Despite the fact that Mount Everest is the tallest mountain above sea level, Mauna Kea is actually much taller than Everest at a total height over 10,000 meters. However, much of it is submerged, with only 4,205 meters rising above sea level.

Dome mountains

Dome mountains are also the result of magmatic activity, though they are not volcanic in nature.

Southeast face of Fairview Dome in Yosemite National Park. Image credits: Jennie.

Sometimes, a lot of magma can accumulate beneath the ground and start to swell the surface. Occasionaly, this magma won’t reach the surface but will still form a dome. As that magma cools down and solidifies, it is often tougher than other surrounding rocks and will eventually be exposed after millions of years of erosion. The mountain is this dome — a former accumulation of magma which cooled down and was exposed by erosion.

Round Mountain is a relatively recently formed dome mountain. It represents a volcanic feature of the Canadian Northern Cordilleran Volcanic Province that formed in the past 1.6 million years. Black Dome Mountain is another popular example, which is also located in Canada.

Other types of mountains

As we mentioned above, there’s no strict definition of mountain classifications, so other types are sometimes mentioned.

Plateau mountains

Plateau mountains aren’t formed by something going up — they’re formed by something going down. For instance, imagine a plateau that has a river on it. Year after year, that river carves out a part of the plateau, bit by bit. After some time, there might only be a small part of the original plateau left un-eroded, which basically becomes a mountain. This generally takes a very long time even by geological standards, taking up to billions of years. Some geologists group these mountains with dome mountains into a broader category called erosional mountains.

Uplifted passive margins

There’s no geological model to fully explain how uplifted passive margins formed, but we do see them in the world. The Scandinavian Mountains, Eastern Greenland, the Brazilian Highlands or Australia’s Great Dividing Range are such examples, owing their existence to some uplifting mechanism.

Hotspot mountains

The trail of underwater mountains created as the tectonic plate moved across the Hawaii hotspot over millions of years. Image credits: USGS.

Although once thought to be identical to volcanic mountains, new research has shed some light on this belief. Hotspots are volcanic regions thought to be fed by a part of the underlying mantle which is significantly hotter than its surroundings. However, even though that hot area is fixed, the plates move around it — causing it to leave a hotspot trail of mountains.

NASA snaps beautiful picture of Mars as it inches over towards Earth

NASA astronomers captured a beautiful image of Mars on May 12, when the planet was just 50 million miles away from Earth. Bright snow-capped polar regions and rolling clouds above the rusty landscape show that Mars is a dynamic, seasonal planet, not an inert rock barreling through space.

This picture was taken just a few days before the Mars opposition on May 22, when the red planet and the sun will be on exact opposite side of the Earth. Mars circles around the sun on an elliptical orbit, and its approaches to Earth range from 35 to 63 million miles. From now to May 30 Mars will inch in ever closer to 46.8 million miles from us — the closest this planet has been to Earth for the last 11 years. Being illuminated directly by the sun, Mars is especially photogenic and NASA used this opportunity to capture a beautiful shot of the planet.

The most eye-catching features are the thick blankets of clouds, clinging to the planet’s thin atmosphere. They can be seen covering large parts of the planet, including the southern polar cap. The western limbs are early morning clouds and haze, while the eastern part is an afternoon cloud extending for more than 1,000 miles at mid-northern latitudes. The northern polar cap is barely visible, as it’s now late summer in that hemisphere.
Mars Near 2016 Oppostion (Annotated)

The overcast Syrtis Major Planitia is an ancient shield volcano, now inactive. It was one of the first structures charted on the planet’s surface by seventeenth century observers. Huygens used this feature as a reference point to calculate the rotation speed of Mars — one day on the red planet clocking in at 24 hours and 37 minutes.

Hellas Planitia basin extends to the south of Syrtis Major. At about 1,100 miles across and nearly five miles deep, you’d think it’s a tectonic depression, but it was actually formed 3.5 billion years ago when a huge asteroid crashed into Mars. The planet had its fair share of meteorite impacts throughout the ages, as Arabia Terra can attest — this 2,800 mile upland region is dotted with craters and heavily eroded. Dry river canyons wind through the region, testament to rivers that once flowed into the large northern lowlands.

The long, dark ridges running along the equator south of Arabia Terra, are known as Sinus Sabaeus (to the east, not pictured) and Sinus Meridiani (to the west). These areas are covered by dark bedrock and sand ground down from ancient lava flows and other volcanic features. The sand is coarser and less reflective than the fine dust enveloping the planet, making them stand out.

Several NASA Mars robotic missions, including Viking 1 (1976), Mars Pathfinder (1997) and the still-operating Opportunity Mars rover have landed on the hemisphere visible in this picture. Spirit and Curiosity Mars rovers landed on the opposite side of the planet.

All images provided by Hubble Site.

Volcanic twins of the Red Sea: Sholan and Jadid

We tend to think of the planets as static, enduring, and never changing. With the average human life spanning only decades, we can be forgiven that the dimension of time in which geological processes take place goes a bit over our heads. However, recent images captured by satellites showing the birth of two volcanic islands published in a study by Nature Communications are a powerful reminder that the Earth is a planet alive under its crust as well as above.

We’re gonna need a bigger diaper.
Image via arstechnica.com

The two islands, named Sholan and Jadid formed during volcanic eruptions in the Zubair archipelago in 2011 and 2013, respectively. They provided an excellent opportunity for scientists to study a rare and not fully understood phenomenon: the creation of land by submarine eruptions. Only a few such eruptions have been witnessed since the emergence of Surtsey Island to the south of Iceland in the 1960s.

Using high-resolution optical satellite images, the study charts the rapid growth of the new islands during their initial eruptive phases and how their shape changes as the waves wash over their coasts: they are being eroded fast by the waters of the Red Sea, one of the islands losing over 30% of its surface in just two years.

The southern part of the Red Sea is a new ocean-to-be, forming as tectonic plates spread apart at about 6mm per year. Under its waters a range of mountains created by volcanic eruptions, an embryonic mid-ocean ridge, forms at the point where these two plates’ boundaries are closest. The structure spreads following the system that feeds the eruptions, magma-filled cracks called dykes.

Tectonic spreading, with magma rising to the surface and mid-ocean ridge formation.
Image via www.divediscover.whoi.edu

Seismic activity similar to that recorded during the islands’ formation has also been recorded in the past, but without emersion of new land. Scientists suggest that this is caused by underwater eruptions or the formation of new intrusive structures in the crust (such as dykes), suggesting that this area is more volcanically active than previously thought.

Looking at the satellite captured images and data pertaining to ground deformation geologists discovered that while the islands measure in at about 1-km in diameter the dykes are at least 10-km in length. This is similar to other areas where spreading takes place, such as Iceland, where geological activity becomes focused around a few vents as the eruption progresses, supporting their claim that active tectonic spreading is taking place in the area.

Sholan and Jadid’s creation has provided scientists with valuable insight into geological processes, but perhaps more importantly, their birth reminds us that the ground underneath our feet was born, lives and one day will return to the earth. It’s alive. Just like us.

 

Mount Ruapehu is the highest mountain on the North Island.

Mount Doom from LOTR set to erupt – in real life

Mount Ruapehu is the highest mountain on the North Island.

Mount Ruapehu is the highest mountain on the North Island.

For his fantastic Lord of the Rings trilogy, director Peter Jackson relied on two volcanoes in New Zealand, Mount Ngauruhoe and Mount Ruapehu, to portray Mount Doom. The latter, however, is keen on showing that it can be bad off-screen as well, after geologists warn that it’s nearing an impending eruption.

“The current situation can’t continue, Ruapehu is so active that the temperatures have been going up and down a lot,” DOC volcanic risk manager Harry Keys told Radio New Zealand.
“They generally haven’t gone up as we’ve expected for some weeks now and sooner or later that situation will be rectified, either in a small, relatively passive way, or with a significant eruption.”

Temperature measurements from a few hundred meters below the lake that sits in the mountain’s crater range at around 800 degrees Celsius (1,472 Fahrenheit), however the water temperature of the lake itself lies only at 20 degrees Celsius. This is a clear sign, according to geologists, that a vent was partially blocked, leading to increased pressure that made eruptions more likely “over the next weeks to months”.

The Department of Conservation (DOC) warns tourists not to stray too close to Ruapehu. The biggest concern, as with all volcanic eruptions, lies with lahar — an avalanche-like wave of ash, mud, gravel and debris, triggered by volcanic activity. Ruapehu’s last eruption was in 2007, when a steaming lahar rushed down hill, causing no injuries fortunately. In 1953, however a massive lahar from the mountain caused New Zealand’s worst rail disaster when it washed away a bridge at Tangiwai and a passenger train plunged into the Whangaehu River, claiming 151 lives.

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methane eruption undersea

200 million years ago, half of all life on Earth went extint from a methane eruption

methane eruption underseaAround 200 million years ago, the Earth was still one big continent – the great Pangaea. Around that time came, what’s commonly referred to as, the End-Triassic mass extinction period in which half of all marine life on the planet went extinct. For years, scientists believed that this came as a result of a mass volcanic eruption across the world, as the massive continent split into multiple segment-continents.

A new study, published just recently in the journal Science, concludes, however, that responsible for the mass extension is actually a deadly methane eruption in the sea floor. Researchers at the Nordic Center for Earth Evolution at the University of Copenhagen claim that as a huge quantity of methane being released into the atmosphere, it killed off much of the species on Earth and paved the way for the age of dinosaurs.

Earth scientist Micha Ruhl and colleagues examined ancient plant fossils sampled from the bottom of the Tethys Ocean, and based on their molecular analysis it appears that “at least 12,000 gigatons of methane was injected into the atmosphere over just 10- to 20,000 years of the end-Triassic extinction.”

The sea floor eruption seems to have went on “burping” for at least 600,000 years, scientists observed. Although it stays in the atmosphere for a briefer period, methane is a more potent greenhouse gas than carbon dioxide and when released outside in the atmosphere, it triggers the release of more methane. A snow-ball effects is thus achieved, which might explain the prolonged duration of the emissions.

According to a release about Ruhl and his team’s findings:

The researchers suggest that this short-lived burst of methane was more likely responsible for the mass extinctions. Changes in vegetation at the end of the Triassic Period also provide evidence of strong warming events and an enhanced global water cycle at the time, they say. Ruhl and his colleagues also say that their findings may help scientists plan ahead, since humans could potentially contribute 5,000 gigatons of carbon or more to the atmosphere if we were to burn all of our known fossil fuel reserves.

However, this doesn’t change any theories about how the dinosaurs went extinct. Just last week the youngest dinosaur fossil was found, which added considerable weight to the already prevailing asteroid mass extinction theory.

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Underwater volcanoes beneath the Antarctic seas. The peak in the foreground is thought to be the most active, with eruptions in the past few years. (c) British Antarctic Survey

Hugely tall underwater volcanos discovered

In the first ever-survey of its kind, geologists have managed to discover a chain of massive underwater volcanoes, some as tall as 2 miles, underneath the Antarctic waters near the South Sandwich Islands in the remote Atlantic Ocean.

The South Sandwich Islands have always been known for their evident volcanic activity, ever since their discovery by famous explorer Captain Cook in 1775. What happens beneath the islands however remained more or less ignored, until recently when scientists mapped in great detail the area of the seafloor around these islands.

Underwater volcanoes beneath the Antarctic seas. The peak in the foreground is thought to be the most active, with eruptions in the past few years. (c) British Antarctic Survey

Underwater volcanoes beneath the Antarctic seas. The peak in the foreground is thought to be the most active, with eruptions in the past few years. (c) British Antarctic Survey

Scientists used sonar scanners to trace each shape and slope of the volcanoes, which fed them back some incredible data – 12 new undersea volcanoes, some topping even two miles. Some are still active, while others have been found collapsed in craters as large as 3 miles.

The volcanoes came as a consequences, scientists claim, of the tectonic dance between the South American continental plate sliding under the South Sandwich plate to the east. Water gets slipped beneath one of the plates and deep into the interior of the earth, from where it escapes upward, springing a molten rock eruption along the way.

Underwater volcanoes form parallel to the plane lines and as they steadily build up, they form new crust which will eventually someday after millions of year link with a continent. Scientists hope to learn more by studying the process in greater detail, and gain a greater grasp upon the formation of continents.

“We have GPS data to show that the South Sandwich Islands are moving east very fast indeed with respect to Africa,” Ian Dalziel of the University of Texas at Austin said. “It’s a very active system.”

Researchers warn however that underwater volcanoes could cause highly damaging tsunamis, since such volcanoes often have unstable slopes.

“This is quite well known,” Phil Leats of the British Antarctic Survey who led the new efforts said “Clearly this has happened in this area. We can see the scars. We can see the quite large slump deposits, which must have caused quite large tsunamis, so clearly it’s an area where this kind of hazard does exist.”

The survey was made by the  British Antarctic Survey.

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Spledid photos from the Sakurajima volcano eruption

Sakurajima is probably the most active and dangerous volcano in Japan. Actually, one of its eruptions from back in 1914 is still attested as the the most powerful volcanic eruption in Japanese history, which at the time engulfed a whole city in ash and lava, and joined the former island with the neighboring Osumi Peninsula.

Photo by Kimon Berlin.

Curious to find more about Sakurajima, in came instead across some incredible photographs taken by alien landscape photographer Martin Rietze, who managed to capture Sakurajima in its full elemental splendor. I’m still left short of words after glaring through them for the past hour now, so I’ll just leave you with these beauts right below. As a small notice, the lightning you see next or through the lava is by no meas a Photoshop effect. What actually happens is that fast moving fine ash causes the flashing lightining – the more plume there is, the more intense the lightning gets. For a conclusive example check out this photo of last year’s eruption from Shinmoedake peak.

 

 

 

 

 

 

 

 

 

Volcanoes played an important role in the origin of life, scientists say

Jeffrey Bada holds a preserved sample containing amino acids created by a 1958 experiment done by his mentor Stanley Miller. (c) Scripps Institution of Oceanography, UC San Diego.

In 1953, chemists Harold Urey and Stanley Miller conducted one of the most famous experiments of the past century, commonly known as the primordial soup, in which they tried to find out how the first sings of life on Earth surfaced by exposing a mix of gases to a lightning-like electrical discharge to create amino acids. Amino acids are very important because they form proteins, which, in turn, form cellular structures and control reactions in living things.

Five years later, in 1958 Miller tried another variation to his experiment by adding to his initial variant hydrogen sulfide, which is spewed by volcanoes. For some reason, the chemist never got around to analyze his results and for last five decades the vile has been shelved away. Jeffrey Bada, Miller’s former student and a Scripps Institution of Oceanography, UC San Diego professor of marine chemistry, discovered the hydrogen sulfide variant of the experiment in Miller’s old lab after he inherited it (Miller passed away in 2007) and analyzed the data with modern equipment and techniques.

The results were remarkable! While Miller’s initial famous experiment concluded the mixture will turn up five organic molecules (amino acids), but the hydrogen sulfide compound combined with light delivered a staggering number of promising molecules: 23 amino acids and four amines, another type of organic molecule. This suggests that volcanic eruptions coinciding with lightning may have played a role in synthesizing a large number of crucial life molecules, and that there may have been a much more abundant variety of organic compound in the early Earth than scientists initially believed.

“Much to our surprise the yield of amino acids is a lot richer than any experiment [Miller] had ever conducted,” says Bada.

Another remarkable finding is that the amino acids in the hydrogen sulfide experiment very much resembles the ones found in asteroids, according to Bada.

It’s somewhat strange trying to figure out why Miller never went around to analyze this sample, but Eric Parker, part of Bada’s team, believes that the “rotten egg”-like odor of hydrogen sulfide is responsible for the shelving.

“When I was working with them by hand I could smell them myself,” Parker said. “It wasn’t so strong that it was overpowering, but it was strong enough to convince me to not stick my nose in front of it again.”

Unpleasant odors aside, the experience was a memorable one.

“It is sort of surreal to hold the sample vial in your hands and look at Stanley Miller’s handwriting on the label,” Parker said. “It was a very unique opportunity to go back in time and look at what he did and be able to use modern analysis techniques to be able to analyze samples produced over 50 years and see what they still contain today.”