Movement of Rock Builds Mountains 3.1 Notes Movement of Rock Builds Mountains

Think about… How can a solid (like rock) fold?

Most mountains form along plate boundaries The rocks on top of Mount Everest contain the remains of ocean animals and rock that formed far away at a seafloor spreading center. Why might this be?

Most mountains form along plate boundaries A shallow sea once covered the area that is now Mount Everest. When an oceanic plate collides with a continental plate, it sinks. As the oceanic plate sinks, some sea-floor material can scrape off onto the continental plate.

Most mountains form along plate boundaries As continental mountains form, that material that was once on the sea floor is now on the top of a mountain!

Mountain ranges and belts A mountain is an area of land that rises steeply from the land around it. A single mountain is rare. Most mountains belong to ranges-long lines of mountains that were formed at about the same time and by the same processes.

Mountain ranges and belts Mountain ranges that are close together make up mountain belts. The Rocky Mountain belt contains about 100 ranges.

Mountain ranges and belts Most of the world’s major mountain belts are located along tectonic plate boundaries.

Mountains, rocks, and sediment At the same time mountains are being built up, erosion is wearing them down. As long as mountains are pushed up faster than they are worn away, they will continue to grow bigger.

Mountains, rocks, and sediment Young mountains tend to be tall and steep. Older mountains are more rounded and worn away.

Mountains, rocks, and sediment If the tectonic plates were to stop moving, eventually the surfaces of all the continents would be almost completely flat due to erosion.

Mountains can form as rocks fold Rocks can bend when stress is applied slowly over a long period of time. Heat also helps rocks bend.

Mountains can form as rocks fold A folded mountain is a mountain that forms as continental crust crumples and bends into folds. These mountains form as an oceanic plate sinks under the edge of a continent or as continents collide. Example: Himalayas

Mountains can form as rocks fold The Himalayas were formed (like many folded mountains) in 3 steps: 1. Convergent Boundary Develops Oceanic lithosphere sank under continental lithosphere. The edge of the continental lithosphere formed folded mountains.

Mountains can form as rock folds 2. Continental Collision Begins Eventually the sea floor was destroyed and two continents began colliding (India and Asia). Volcanoes stopped erupting and the mountains were pushed up further.

Mountains can form as rock folds 3. Collision Continues The two continents continue to push the rocks up into mountains that grow taller each year.

Mountains can form as rock folds Earthquakes at continental-continental collision zones can also contribute to the upward growth of mountains in these locations.

Mountains can form as rocks move along faults Mountains that form as blocks of rock move up or down along normal faults are called fault-block mountains. In the Southwest U.S., hundreds of fault-block mountain ranges line up in parallel rows that coincide with parallel normal faults.

Mountains can form as rocks move along faults There are two steps to the formation of fault-block mountains. 1. An area of lithosphere arches upward and breaks into blocks separated by faults as it is heated by the mantle below

Mountains can form as rocks move along faults 2. As the lithosphere is pulled apart, some blocks tilt to form mountains and valleys. Other blocks drop down between faults.

Mountains can form as rocks move along faults Fault-block mountains form as stress is repeatedly released through earthquakes. Even the most powerful earthquakes only move rocks a small number of meters. It take millions of years and countless earthquakes to build up large fault-block mountain ranges!

Mountains can form as rocks move along faults All mountains take millions of years to form and erode away.

review In areas where the lithosphere is being pulled apart, the crust Folds and crumples into mountains Breaks into blocks separated by faults Slides down into the mantle Develops a subduction zone

review 2. When two plates carrying continental crust collide, the rock of the continents Folds Melts Expands Stretches

review 3. The movement of huge blocks of rock along a fault can produce Lava plugs Volcanoes Fault-block mountains Folded mountains