Just an add-on for anyone who is interested in learning more tectonic plates and the Ring of Fire.

Plates & Boundaries

The earth's continents are constantly moving due to the motions of the tectonic plates. Closely examine the map, which shows the 15 major tectonic plates. (see thumbnail)

As you can see, some of the plates contain continents and others are mostly under the ocean. The type of crust that underlies the continents is called continental crust, while the type found under the oceans is called oceanic crust. Continental crust is thicker — about 20 to 40 miles (35 to 70 km) thick — and usually older than oceanic crust, which is only 4 to 6 miles (7 to 10 km) thick. All the plates have names, usually referring to landmasses, oceans, or regions of the globe where they are located.

The border between two tectonic plates is called a boundary. All the tectonic plates are constantly moving — very slowly — around the planet, but in many different directions. Some are moving toward each other, some are moving apart, and some are sliding past each other. Because of these differences, tectonic plate boundaries are grouped into three main types.

As you might expect by now, most major geologic events occur at the boundaries between tectonic plates, where huge, massive pieces of the earth's crust interact. Each kind of plate boundary is associated with particular events, so if you know about the movements taking place at a plate boundary, you can often predict what's likely to occur there — volcanoes, earthquakes, mountains, trenches — in the future!

At convergent boundaries, tectonic plates collide with each other. The events that occur at these boundaries are linked to the types of plates — oceanic or continental — that are interacting.

Subduction Zones and Volcanoes

At some convergent boundaries, an oceanic plate collides with a continental plate. Oceanic crust tends to be denser and thinner than continental crust, so the denser oceanic crust gets bent and pulled under, or subducted, beneath the lighter and thicker continental crust. This forms what is called a subduction zone. As the oceanic crust sinks, a deep oceanic trench, or valley, is formed at the edge of the continent. The crust continues to be forced deeper into the earth, where high heat and pressure cause trapped water and other gasses to be released from it. This, in turn, makes the base of the crust melt, forming magma.

The magma formed at a subduction zone rises up toward the earth's surface and builds up in magma chambers, where it feeds and creates volcanoes on the overriding plate. When this magma finds its way to the surface through a vent in the crust, the volcano erupts, expelling lava and ash. An example of this is the band of active volcanoes that encircle the Pacific Ocean, often referred to as the Ring of Fire.

A subduction zone is also generated when two oceanic plates collide — the older plate is forced under the younger one — and it leads to the formation of chains of volcanic islands known as island arcs. Examples include the Mariana Islands in the western Pacific Ocean and the Aleutian Islands, off the coast of Alaska.

Since the collision and subduction of plates is not a smooth process, large, powerful earthquakes are another phenomenon that result from this type of interaction. Earthquakes generated in a subduction zone can also give rise to tsunamis. A tsunami is a huge ocean wave caused by a sudden shift on the ocean floor, such as an undersea earthquake. If the wave reaches land, it can cause incredible destruction, like the Asian Tsunami, which killed more than 200,000 people in 11 countries across the Indian Ocean region in December 2004.

Collision Zones and Mountains

What happens when two continental plates collide? Because the rock making up continental plates is generally lighter and less dense than oceanic rock, it is too light to get pulled under the earth and turned into magma. Instead, a collision between two continental plates crunches and folds the rock at the boundary, lifting it up and leading to the formation of mountains and mountain ranges.

An example of this mountain-building process is the Himalayan range in southern Asia. Containing the highest mountain peaks in the world and traversing the modern-day countries of India, Pakistan, China (Tibet), Bhutan, and Nepal, the Himalayas were formed by the collision of the Indian and Eurasian Plates. This process began after the breakup of Pangaea, when India became an island continent and began traveling northward toward Asia. The island of India slammed into Asia about 40 to 50 million years ago near modern-day Tibet, crushing and folding the plates to form the Himalayan mountain range. Its best known peaks, Mount Everest and K2, are among several that measure over 8,000 meters (26,000 feet) high at their summits. Since the Indian Plate is continuing in its northward movement into Asia, the Himalayas continue to grow higher each year by small amounts (5 to 20 mm or 1 inch per year).

How Plates Move
Powered by forces originating in Earth’s radioactive, solid iron inner core, these tectonic plates move ponderously about at varying speeds and in different directions atop a layer of much hotter, softer, more malleable rock called the athenosphere. Because of the high temperatures and immense pressures found here, the uppermost part of the athenosphere is deformed and flows almost plastically just beneath the Earth’s surface. This characteristic of the athenosphere to flow allows the plates to inch along on their endless journeys around the surface of the earth, moving no faster than human fingernails grow.

The Ring of Fire
In the not too distant past, cartographers charted the deep ocean trenches, seismologists plotted earthquakes beneath the trenches, and volcanologists studied the overlying volcanoes. But these researchers worked independently of each other, and were unaware that the phenomena they studied were all part of a singular process. Today, the ideas of sea-floor spreading and subduction explain clearly why so many of the world’s volcanoes are situated on the Pacific island arcs, the Ring of Fire, where earth’s tectonic plates are being subducted beneath deep ocean trenches.

After about 10 million years, the final stage of subduction begins. At depths of as much as 450 miles, the plate becomes so hot that it softens and stops generating earthquakes. But the descent and melting continue until, at some unknown depth, the plate blends with the surrounding mantle material. Eventually this material will emerge along Mid-Ocean Ridges as new sea-floor crust or escape as volcanic lava as the process of subduction comes full circle and our tectonic planet continues to evolve.

Well it's a lot of information but for those interested in the scientic explaination of our living planet in motion, I thought to share some of the information that I had. :)

Love and blessings,
Angelita