RESTLESS EARTH - CHAPTER 4

Transcription

1 RESTLESS EARTH - CHAPTER 4 continental crust - Composition is similar to granite and forms the continents and the areas of shallow seabed. oceanic crust - Composition similar to basalt. It is thinner, denser, and younger than the continental crust.

2 Structures of the Earth: crust - The outermost layer of the Earth. It is also the thinnest layer of the Earth. mantle - This is the layer of the Earth between the crust and the core. It is extremely thick and contains most of the Earth s mass. core - The core extends from the bottom of the mantle to the center of the Earth. It is made mostly of iron, with smaller amounts of nickel and possibly some sulfur and oxygen. outer core - The liquid layer of the Earth s core that lies beneath the mantle and surrounds the inner core. inner core - This is the solid, dense center of our planet that extends from the bottom of the outer core to the center of the Earth.

3 lithosphere - The outermost, rigid layer of the Earth. This is made up of the crust and the upper part of the mantle. The lithosphere is divided into pieces called tectonic plates. asthenosphere - weak sphere A soft layer on the mantle on which pieces of the lithosphere move. It flows very slowly. mesosphere - A strong lower part of the mantle. It extends from the bottom of the asthenosphere down to Earth s core.

4 Tectonic Plates: Pieces of the lithosphere that move around on top of the asthenosphere. These are pieces of a jigsaw puzzle. continental drift : A theory that continents can drift apart from one another and have done so in the past. It also explained why fossils of the same plant and animal species are found on both sides of the Atlantic Ocean. Ancient species could not have made it across the ocean. It explained puzzling evidence left by ancient glaciers. atest-discoveries-continental-drift/ Sea-floor spreading - The process by which new oceanic lithosphere is created as older materials are pulled away. As tectonic plates move away from each other, the sea floor spreads apart and magma rises to fill in the gap. THE THEORY OF PLATE TECTONICS

5 plate tectonics : The theory that the Earth s lithosphere is divided into tectonic plates that move around on top of the asthenosphere. Convergent Boundaries : When two tectonic plates push into one another, the boundary where they meet is called a convergent boundary. Divergent Boundaries : When two tectonic plates move away from one another, the boundary between them is called a divergent boundary. Transform Boundaries : When two tectonic plates slide past each other horizontally, the boundary between them is called a transform boundary. The San Andreas Fault in California is a good example. Deforming the Earth s Crust

6 Stress : The amount of force per unit area that is put on a given material. Example: With a small amount of stress, uncooked spaghetti bends. Additional stress causes it to break. Compression : The type of stress that occurs when an object is squeezed (two tectonic plates collide). Tension : A form of stress that occurs when forces act to stretch an object. Folding : This occurs when rock layers bend due to stress in the Earth s crust. Fault : The surface along which rocks break and slide past each other is called a fault. The position of the fault block determines whether it is a hanging wall or a footwall. Normal Fault : The movement of a normal fault causes the hanging wall to move down relative to the footwall.

7 Reverse Fault : The movement of a reverse fault causes the hanging wall to move up relative to the footwall. Strike-Slip Fault : This occurs when opposing forces cause rock to break and move horizontally. The ground would appear to move left or right.