STEM

Unit 4 earths processes

**Geologists**

scientists who study the Earth, the materials that make it up, and how it has changed over time.

**Crust** 

Earth’s outermost layer; covers Earth’s entire surface; ranges in thickness from 6 km (under the ocean – made of basalt) to 90 km (under continents – made of granite). 

**Continents**

large land masses

**Mantle**

 layer under the crust; thickest layer – makes up most of Earth’s mass; made of rock containing iron and magnesium; the upper part is rigid and the lower part flows slowly.

**The core**

center layer is made up mostly of the metals iron and nickel.

**Outer Core**

is liquid and flows slowly

**Inner Core**

is solid and under great pressure; hottest layer.

**Conduction**

 transfer of heat energy through solids. This is how heat moves through the core and the crust.

**Convection**

transfer of heat energy through flowing material, like liquid or gas. This is how heat moves in the mantle. (Matter in the lower mantle heats up and expands, becomes less dense, rises, and is pushed upward by cooler, denser material. As the material rises, it cools down, becomes denser, and sinks back down where it is heated again and the cycle repeats.

**Convection Currents**

The cycling of heated matter due to the changes in density. It occurs in the mantle and causes many changes on Earth’s surface.

**Fossils**

remains imprints or traces of living things from long ago.

**Pangaea**

the supercontinent, when all the continents were joined together as one.

**Continental Drift**

 the idea that continents move from one part of the Earth to another.

**Lithosphere**

 Earth’s crust and upper mantle; the brittle, outer layer of Earth. It is solid, but it moves.

**Plates**

 moving sections of the lithosphere; made up of a dozen large ones and some smaller ones; made of both oceanic and continental crust.

**Asthenosphere**

underneath the lithosphere; an area of the upper mantle’ solid but hot enough to bend and change shape. It moves because of convection currents, which makes the plates sitting on top of it move also.

**Plate Tectonics**

the theory that explains how and why plates move.

**Sonar Mapping**

ships bounce sound waves off the ocean floor, which helps to figure out the depth of the ocean, by using the time a sound is sent and when the echo is received. Used to map the ocean floor.

**Mid-ocean ridge**

1.  long, narrow chain of mountains rising from the ocean floor; an underwater mountain range.

**Rift**

the valley that runs along the crest of the mid-ocean ridge.

**Magma**

Melted rock

**Trenches**

1. narrow, deep areas of the ocean floor at the edges of plates. This is where the old oceanic crust is destroyed when it is forced under another plate.

**Subduction**

the sliding of one plate under another one, forcing it into the mantle where it will melt. This occurs in trenches.

**Sea-floor spreading**

the process of oceanic crust being created at the mid-ocean ridge, moving sideways away from the ridge, and being pushed back or subducted into the mantle at a trench. This led to the developing and accepting the Theory of Plate Tectonics.