Online:
Visits:
Stories:
Profile image
By Universe Today (Reporter)
Contributor profile | More stories
Story Views

Now:
Last Hour:
Last 24 Hours:
Total:

How Do Volcanoes Erupt?

Thursday, May 26, 2016 12:41
% of readers think this story is Fact. Add your two cents.

(Before It's News)

Cleveland Volcano Eruption

Volcanoes come in many shapes and sizes. Ranging from the common cinder cone volcanoes that build up from repeated eruptions, to large, broad shield volcanoes; from lava domes that pile up over volcanic vents, to composite volcanoes that combine features of more than one. Though they differ in terms of structure and appearance, they all share one thing in common. Basically, all volcanoes are created by of the same force of nature. What this comes down to is magma from beneath the Earth reaching the surface and erupting as lava, ash and rock. But what mechanism drives this process? What is it exactly that makes this molten rock rise from the Earth’s mantle and explode onto the landscape? To understand how volcanoes erupt, you need 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. 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 to 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. Another mechanism that drives volcanism is geological activity. To break it down, the lithosphere is also divided into several plates, which are constantly in motion atop the mantle.  This activity is what drives geological activity, which includes earthquakes and volcanoes. Sometimes the plates collide, pull apart, or slide alongside each other; resulting in convergent boundaries, divergent boundaries, and transform boundaries. 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. In the mantle region, conditions changes drastically from the crust. Pressures increase considerably and temperatures can reach more than 1000 °C, which makes the rock semi-viscous enough that it behaves elastically on time scales of thousands of years or greater. Whereas this layer, which is largely composed of silicate rock, is mostly in solid form, pockets of molten rock are common. 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. With each eruption, rocks, lava and ash build up around the volcanic vent where the material blasts out of. The nature of the eruption depends on viscosity of the magma. When the lava flows easily, it can travel far and creates wide shield volcanoes. When the lava is very thick, it creates a more familiar cone volcano shape. When the lava is extremely thick, it can build up in the volcano and explode. 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. We have written many articles about volcanoes here at Universe Today. Here’s What are the Different Types of Volcanoes?, What are the Different Parts of a Volcano?, 10 Interesting Facts About Volcanoes?, What is the Pacific Ring of Fire?, Olympus Mons: The Largest Volcano in the Solar System. Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth. We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

The post How Do Volcanoes Erupt? appeared first on Universe Today.



Source: http://www.universetoday.com/31124/how-volcanoes-erupt/

Report abuse

Comments

Your Comments
Question   Razz  Sad   Evil  Exclaim  Smile  Redface  Biggrin  Surprised  Eek   Confused   Cool  LOL   Mad   Twisted  Rolleyes   Wink  Idea  Arrow  Neutral  Cry   Mr. Green

Top Stories
Recent Stories

Register

Newsletter

Email this story
Email this story

If you really want to ban this commenter, please write down the reason:

If you really want to disable all recommended stories, click on OK button. After that, you will be redirect to your options page.