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4 Layers of the Earth

Crust, Mantle, Outer Core, Inner Core


thinnest layer, mostly solid rock, cool at top and hot at bottom


thickest layer (takes up about 2/3 of Earth's volume), molten rock that flows like syrup

Outer Core

thick layer, made up of liquid iron and nickel

Inner Core

thinner layer, made up of solid iron and nickel (due to extreme pressure), hottest layer


The supercontinent that formed 200 million years ago that included all of the land masses known to be on Earth at that time

Continental Drift

the theory that states all continents are on large plates that moved and carried the continents to their current positions

Four reasons scientists think Pangaea existed

Rock formations are the same on different continents; Mountain formations are the same age; Fossil evidence of plants and animals; Glacier and fossil evidence

Plate tectonics

a theory that the Earth's crust is made up of many plates that move slightly as they gloat on the mantle, driven by the Earth's heat energy (convection currents)

CONVERGENT boundaries

Boundaries where plates come together or meet.

Subduction zone

What is formed when one plate moves under another.

Ocean trenches and volcanic islands are formed when

an oceanic and a continental plate come together.

Mountains are formed when

two continental plates come together.

DIVERGENT boundaries

Boundaries where plates split or come apart. The spreading allows magma from the mantle to form new crust.

Transform Fault Boundary

Boundaries where plates grind or slide past one another. Also known as a "strike-slip" boundary. Earthquakes can occur.


a jolting that occurs when two plates try to move past one another. These are caused by plate movement.


the weak point of fracture in the Earth's surface where the rock layers have ruptured and/or slipped. (This is where most earthquakes and volcanoes are located.)

Richter Scale

a scale based on the numbers one to ten, that measures the energy released in an earthquake.


a machine that measures earthquakes, allows us to locate the epicenter.


hot molten rock; it escapes through an opening in the Earth's crust.


magma that reaches the Earth's surface and piles up around volcanoes.


a wave of water that sometimes follows earthquakes or volcanoes.

Ocean Floor Spreading

currents on the magma pushing the ocean floor apart. Ocean ridges are formed.

Ring of Fire

a major earthquake zone that forms a circle around the Pacific Ocean.


a mountain that forms when lava, ashes, rocks and melted materials pile up and harden.


rocks made from magma. Usually made of mineral crystals of different sizes. Often has pores or holes in it.

Examples of Igneous rocks are

granite, basalt, obsidian


rocks made from dirt, sand, and pieces of rock. Often formed in layers and often contain fossils.

Examples of sedimentary rocks are

sandstone, limestone


rocks changes by heat or pressure

Examples of metamorphic rocks are

marble, slate


The breaking down of rocks and other materials on the Earth's surface.


the process that moves weathered material from one place to another

The two kinds of weathering are

Physical and Chemical

Physical Weathering

The breakdown of rocks into smaller pieces without changing the type of material.

Example of physical weathering is

"frost wedging," caused by water that seeps into small cracks and freezes; the frozen water expands, forcing the crack to enlarge.

Chemical Weathering

The breaking down of rock by changing what it is made of.

Example of chemical weathering is

oxygen combining with certain minerals, and oxidation forms new substances or oxides, such as rust.

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