Earth on the Move Earth Structure Plate Tectonics

Earth on the Move Earth Structure & Plate Tectonics Notes Baker 7 th grade science 20032004

Earth, Inside & Out n 1. 2. 3. The Earth is divided into three layers Crust Mantle Core Baker 7 th grade science 20032004

Crust n n n (1) This is the outermost layer of the Earth. (2) This is the layer we walk on. (3) It is a thick, rocky skin. (4) If we think of the Earth as a billiard ball, this crust is as thin as a postage stamp stuck on a billiard ball. (5) At its thickest, which is under mountain ranges, the crust is only about 35 km (22 mi) thick. Baker 7 th grade science 20032004

And what type of crust would you like with your Earth? n There are two types of crust Baker 7 th grade science 20032004

Continental Crust: 1. Makes up the continents n 2. Contains light colored rocks such as granite. n 3. Floats high on the mantle n Baker 7 th grade science 20032004

(i) Oceanic Crust 1. Makes up the ocean floor n 2. Contains the dense rocks such as basalt n Thinner than the continental crust n Baker 7 th grade science 20032004

Mantle (1) Hotter and denser than the crust because the deeper you go inside the earth, the temperature & pressure increases. n (2) Made of solid rock. n The Mantle is made of two zones n Baker 7 th grade science 20032004

Mantle Zones (a) Lithosphere n (i) Thin, uppermost part of the mantle; cooler & less rigid n (ii) Floats on the athenosphere, and slides around very slowly. n (iii) The upper part of the lithosphere melts rocks, forming a substance called magma. n Baker 7 th grade science 20032004

Magma 1. Magma (melted rock) moves like hot oatmeal. n Uneven heating causes material in the mantle to constantly and slowly rise & fall in convection currents. n Convection Current: process by which hot fluid rises to the surface, and then sinks again, like soup being heated in a saucepan n Baker 7 th grade science 20032004

(a) Asthenosphere Hot, weak zone directly under the lithosphere n Flows at a very slow rate n Baker 7 th grade science 20032004

Core i) Deep within the Earth is the core n ii) The core is made mostly of nickel & iron n iii) Twice as dense as the mantle. n Main source of heat that triggers the convection currents n Baker 7 th grade science 20032004

The core is made of two layers (1) Outer core: molten & is responsible for the Earth’s magnetic field. n Inner core: solid n Baker 7 th grade science 20032004