THE EARTH'S INTERIOR and CRUST
|As you go deeper into the earth:
1) The materials it's made of changes
2) The materials increase in density
3) The temperature and pressure increase
|Earth's layers can be classified in different ways.
Here they are classified by physical properties. (Are they hot or cold / liquid or solid?)
They are also classified by what they are made of.
|Layers by Physical Properties
Lithosphere - cool, solid
|Layers by Their Composition
Crust - rocky silicates (5 - 50 km thick)
The crust is made up of three different kinds of rocks. Each kind of rock is formed in a different way. Igneous rocks are formed when melted rock inside the crust cools. As the rock cools, it becomes hard. Usually this rock is formed from volcanoes. Sedimentary rocks are formed when material is eroded by water and weather. This material settles and hardens. Sedimentary rock may contain fossils. Metamorphic rocks form from a change. Heat and the weight of the earth's crust change igneous and sedimentary rocks into metamorphic rocks.
Soil is found on the crust. It is made from the breakdown of rocks
and the decay of dead organisms. Soil nourishes plants and contains living
Because the crust floats on the mantle, movement occurs between different parts of the crust. This movement creates forces that sometimes cause earthquakes and volcanic eruptions. The entire crust is made up of plates called tectonic plates. As these plates float on the mantle, theu sometimes brush or bump into each other. This kind of movement causes earthquakes. When the plates float away from each other, they leave gaps or vents, through which melted rock (magma) from the mantle seeps or gushes to the surface. This movement of melted rock to the surface is a volcanic eruption.
Evidence for the theory
of Plate Tectonics:
Shape of the continents - they seem to fit together
There is fossil evidence
continents were once together.
There is rock evidence that continents were once together.
There is glacier evidence that continents were once together.
|Sea floor spreading - the mid-ocean ridge is a
huge crack in the crust where the hot mantle pushes upward. Pieces of the
crust on each side of the crack move away from each other. Molten
rock from the mantle wells up, forming new crust.
Old crust is being swallowed up in ocean trenches at the same time so the ocean bottom is recycled every 300 million years.
Theory of plate tectonics - the lithosphere of the earth is divided into plates which are constantly moving.
Plates meet at boundaries
Plates can be convergent (plates come together)
Plates can be divergent (plate move away from each other)
Plates can have transform faults (plates slide past each other)
This causes earthquakes and volcanoes, as well as mountain building. Earthquakes, volcanoes, mountains occur at plate boundaries.
Convection in the mantle makes the plates move.
Sometimes, however, the Earth builds up instead of tearing down as it changes. Many mountain ranges have been pushed up out of the earth as tectonic plates brushed past one another and earthquakes occurred. Many islands in the ocean have been built up as a result of volcanic eruptions. The Hawaiian Islands formed when volcanoes erupted. The melted rock boiled through open spaces in the crust. Then it came in contact with the ocean, which cooled and hardened it. With each eruption, more rock was added until the islands were above sea level. Gradually the rock broke down into soil and plants began to grow. Through its mightly forces, the Earth can be destructive, but it also can be constructive.
1. What is the outer layer of Earth? _____________________________________________________
2. How thick is the crust? ____________________________________________________________
3. How does the crust rest on the Earth? ________________________________________________
4. What kinds of rock make up the outer layer of the earth. How is each type formed? _____________
5. What are the two major forces that change the shape of the earth's crust? ______________________
6. Describe the force that causses an earthquake? _________________________________________
7. What force causes a volcanic eruption? _______________________________________________
8. How do earthquakes and volcanic eruptions affect the people who live near them? _______________
Discuss the Richter
FOR THE GEPA: The state says you need to know the following:
A student should know that:
A. NATURAL PROCESSES THAT CHANGE THE FEATURES ON THE EARTH'S SURFACE
INCLUDE EROSION, GLACIATION, WEATHERING, EARTHQUAKES, AND VOLCANOES.
1. Dynamic forces change the earth's surface by building up or wearing down.
2. New features on the earth's crust are formed as a result of dynamic forces.
3. The earth's surface can change abruptly as a result of earthquakes and volcanic eruptions or the earth's surface can change more slowly as a result of erosion, glaciation, and weathering.
4. Forces that uplift the earth's surface include volcanism which forms mountains and volcanoes.
5. Forces that wear the earth's surface down include weathering, glaciation and erosion. Features formed as a result of these forces include soil and valleys.
6. Each of these changes has an impact on people.
7. Fossils provide evidence that life and environmental conditions have changed.