You will learn more about volcanoes in the following lessons. As the volcano erupts it may build a mountain. The lava along with ash and other pyroclastic material will continue to build the mountain higher with each eruption. This is a cross section of the Earth in the Southern Hemisphere. The map shows a subduction zone that has created the Peru-Chile Trench at the western edge of South America.
This subduction zone has produced the Andes Mountains which run along the entire west coast of South America. It also shows you the Mid-Atlantic Ridge which is spreading the Atlantic Ocean making it wider and wider. The cross section shows two processes at work;. The pink lines on this map of the Pacific Ocean represent deep ocean trenches. These trenches are some of the lowest points on the crust of the Earth. Marianas Trench north of New Guinea is the deepest point on the Earth's surface at 36, feet below sea level.
Marianas Trench is 7, feet deeper than Mount Everest is high!!!! Trenches surround almost all of the Pacific Ocean. There are trenches wherever continental plates and oceanic plates collide. The Java Trench in the Indian Ocean is the deepest point of that ocean at 24, feet below sea level. Write the answers to the following questions in complete sentences on a piece of paper. Use the page titles located directly under the questions to move your way through the lesson to locate the answers.
When you finish the questions click on the Earth icon to return the program to the beginning. In your own words explain what happens at a subduction zone. In your own words explain what happens at a mid-ocean ridge. At a subduction zone what causes magma to rise? Skip to main content.
Citizen Science Buzz. Frameworks Scientists in Schools. Share this page. RSS Feeds. This image is a cross section through the Earth showing the convection cells of the mantle. Ridge push happens at spreading centers where plates are moving apart. Slab pull happens at subduction zones where one plate is pulled down into the mantle.
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Plate Tectonics The main force that shapes our planet's surface over long amounts of time is the movement of Earth's outer layer by the process of plate tectonics. This picture shows how the rigid outer layer of the Earth, In addition, the diving plate melts and is often spewed out in volcanic eruptions such as those that formed some of the mountains in the Andes of South America. At ocean-ocean convergences, one plate usually dives beneath the other, forming deep trenches like the Mariana Trench in the North Pacific Ocean, the deepest point on Earth.
These types of collisions can also lead to underwater volcanoes that eventually build up into island arcs like Japan. At divergent boundaries in the oceans, magma from deep in the Earth's mantle rises toward the surface and pushes apart two or more plates. Mountains and volcanoes rise along the seam. The process renews the ocean floor and widens the giant basins.
A single mid-ocean ridge system connects the world's oceans, making the ridge the longest mountain range in the world. On land, giant troughs such as the Great Rift Valley in Africa form where plates are tugged apart.
If the plates there continue to diverge, millions of years from now eastern Africa will split from the continent to form a new landmass. A mid-ocean ridge would then mark the boundary between the plates. The San Andreas Fault in California is an example of a transform boundary, where two plates grind past each other along what are called strike-slip faults.
These boundaries don't produce spectacular features like mountains or oceans, but the halting motion often triggers large earthquakes, such as the one that devastated San Francisco. All rights reserved. They move at a rate of one to two inches three to five centimeters per year. Convergent Boundaries Where plates serving landmasses collide, the crust crumples and buckles into mountain ranges. Divergent Boundaries At divergent boundaries in the oceans, magma from deep in the Earth's mantle rises toward the surface and pushes apart two or more plates.
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