The forces that shape the earth begin beneath the lithosphere. Rock in the asthenosphere is hot enough to flow slowly. Heated rock rises, moves up toward the lithosphere, cools and circulates downward. Riding above this circulation system are the tectonic plates, enormous moving pieces of the earth’s lithosphere. [pic]
Tectonic Plates move in four different ways. When tectonic plates come into contact, changes on the earth’s surface occur. 1. Diveregnt Boundary- Plates move apart, spreading horizontally. 2. Convergent Boundary-Plates collide causing either on plate to dive under the other or the edges of both plates crumple. 3. Transform Boundary- Plates slide past one another.
Folds and Faults
When two plates meet each other, they can cause a folding or cracking of the rock. The transformation of the crust by folding or cracking occurs very slowly, often only a few centimeters or inches a year. The rocks, which are under great pressure, become more flexible and bend or fold, create changes in the crust. [pic]
As the plates grind or slip past each other at a fault, the earth shakes or trembles. This sometimes violent movement of the earth is an earthquake.
Magma, Gases and Water from the lower part of the crust or the mantle collect underground chambers. Eventually the materials pour out of a crack into the earth’s surface. Most Volcanoes are found along the tectonic plate boundaries. [pic]
Some Earthquakes causes a tsunami a giant wave in the ocean. A tsunami can travel from the epicenter of a quake at speeds of up to 450 miles per hour, producing waves of 50 to 100 feet higher, [pic]
Weathering Refers to Physical and Chemical processes that change the characteristics of rock on or near the earth’s surface. Weathering occurs slowly over many years and even centuries. Weathering process create smaller and smaller pieces of rock called...