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Earth Science Chapter 7 - Summary Notes
· The Earth is divided into three layers-the crust, mantle and core.
· The crust is the thinnest layer (less than 1% of Earth’s mass) and the layer we live on. Continental crust is thicker but less dense that oceanic crust.
· The mantle is the layer in between the crust and the core. It contains two-thirds of the Earth’s mass. Some of the mantle reaches us through volcanoes, but no one has ever seen what the mantle really looks like.
· The core is even more of a mystery to geologists. It is just a little bigger than Mars.
· Tectonic plates make up the lithosphere, which is the outermost layer of the crust. They divide the earth into puzzle-like pieces.
The theory of continental drift
proposes that the plates have moved away from their original location. Originally, continents like
· It is thought that all of the continents were once a single landmass we call Pangaea.
· Two tectonic plates that slide into each other meet at a convergent boundary. Two tectonic plates that move away from one another form a divergent boundary.
· Two tectonic plates can also slide past one another at a transform boundary. This is the cause of earthquakes.
· Stress is the amount of force per unit area that is put on a given material. Rocks deform, or change shape, due to stress.
· Squeezing stress causes compression. Stretching stress is tension.
· Stress can cause rocks to bend. This activity is called folding.
· Stress can also cause rock layers to break and slide past each other. This creates a fault. Faults and folds are two sources of mountains.