THE CHANGING EARTH
CHAPTER 1: PLATE TECTONICS
I. The Big Idea and Key Concepts
A. Big Idea: The movement of tectonic plates causes geologic changes on Earth.
B. Key Concept 1.1: Earth has several layers.
C. Key Concept 1.2: Continents change position over time.
D. Key Concept 1.3: Plates move apart.
E. Key Concept 1.4: Plates converge or scrape past each other.
II. Section 1.1: Earth has several layers.
1. inner core- a dense ball of hot, solid metals at the center of the Earth
2. outer core- a layer of liquid metals that surrounds the inner core
3. mantle- Earth’s thickest layer (1700 mi.); made up of hot rock that is less dense than the metallic core
4. crust- Earth’s outermost layer; a thin layer of cool rock
5. lithosphere- most rigid of Earth’s layers; includes the crust and the very top of the mantle
6. asthenosphere- layer of hotter, softer rock in the upper mantle
7. tectonic plates- large and small slabs of rock that make up the lithosphere
B. Earth is made up of materials with different densities.
1. How was the Earth formed?
a. Scientists believe the Earth formed 4.6 billion years ago.
b. Then, it was a spinning mass of rocks and dust that was loosely held together.
c. Over time, many comets and asteroids crashed into its surface and added to its mass.
d. Impacts, radioactive decay and gravity produced intense heat.
e. It was a young planet, a glowing ball of melted rock.
f. In time, the denser materials such as iron and nickel sank towards the center. Less dense materials rose to the surface. Other materials settled in between.
g. Earth’s main layers formed.
C. Earth’s layers have different properties.
1. How do we know what Earth is like deep inside?
a. Scientists study energy from earthquakes or underground explosions they set off.
b. Energy moves through Earth like ripples in a pond.
c. Energy moves slower through less dense materials or liquids and faster through denser materials or solids.
2. Core, Mantle, Crust
a. Inner core: solid ball of hot, dense Fe and Ni.
b. Outer core: liquid metal layer that surrounds the inner core.
c. Mantle: thickest layer made of hot, less dense rock. Very top is cool and rigid, lower part is warmer and pasty (soft enough to move).
d. Crust: thin layer of cool rock. It is thinner under oceans, deeper under mountains. Contains all life on Earth.
i. continental crust- continents, major islands
ii. oceanic crust- all ocean floors
e. The crust and the top of the mantle form the lithosphere, the most rigid of all the layers. It sits atop the asthenosphere, hotter, softer rock in the upper mantle. It flows slowly like hot tar.
D. The lithosphere is made up of many plates.
1. The lithosphere is broken into many large and small slabs of rock called tectonic plates.
2. Scientists do not know how or when these giant plates formed.
a. Fit together like a jigsaw puzzle.
b. Large plates include continental and oceanic crust.
c. Most continental crust rises above the ocean; the rest of the plate is oceanic, or underwater.