Layers of the Earth

lithosphere  -- the rock at the Earth's surface forming a nearly continuous shell around the Earth

hydrosphere -- the relatively thin layer of water covering much of the lithosphere
                        (approximately 71% of the lithosphere/earth surface)

atmosphere -- the relatively thin layer of gases surrounding the Earth

**  Only a few minerals make up most of the rocks of the Earth.

Minerals are usually identified based on their physical properties.

Some Physical Properties of Minerals

1.   streak -- the color of the powdered mineral --- may be different than the mineral's color

2.   hardness -- the resistance of the mineral to being scratched

3.  reaction to acid -- some minerals bubble releasing CO₂ when acid is dropped on them

Categories of Rocks

1.   sedimentary rocks -- formed from sediments (small rock particles) being compressed under the ocean into layers

--  Most fossils are found in sedimentary rock.

fossils -- remains or evidence of remains of past life

-- Fossils can be used to study past environments and climates of the Earth, as well as provide an
an approximate age of the rock they are found in.

2.   metamorphic rocks -- formed under great heat and pressure

3.   igneous rocks -- formed from molten rock which has solidified

**  Metamorphic and igneous rocks rarely contain fossils.

The rock cycle model shows how types of rock or rock material may be transformed from one rock type to another.

soil -- consists of sediment, organic material, water, and air

erosion -- the carrying away of weathered material (often sediment)

Gravity is the driving force behind erosion.

Some Agents of Erosion

1.   moving water -- the chief agent of erosion
2.   wind
3.   moving glaciers ( huge sheets of ice)

Water Cycle -- the journey water takes as it circulates from the land to the sky and back again.
 
 

The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapor cools and eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air, precipitation (rain, snow, etc.) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas.

1.   crust -- the relatively cool surface layer of our planet which is divided into separate divisions or plates -- these plates of the earth's crust are moved by the currents of the mantle beneath it 2.  mantle -- is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water. Many geologists believe that the mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over.  3.   Outer core -- formed of very hot (4000 degrees F. to 9000 degrees F.) molten iron and nickel 4.  Inner core -- is as hot as the outer core, but the materials in it are under so much pressure that they act as a solid

-- Convection current movement of material within the Earth may cause sections of the Earth's crust to move and
    provide the driving force for the movement of the plates the Earth's crust is divided into.

Theory of Plate Tectonics -- the "solid" lithosphere consists of a series of plates that "float" on the partially
                                                molten mantle

earthquakes -- may be produced by these movements of the crust

volcanoes -- occur where weaknesses or cracks formed in the earth's crust due to materials moving in
                    the magma allow molten material (called magma underground and lava at the surface) to escape

Crustal movements also form mountains (where they push together) and ocean basins and trenches (where they
spread apart.

The crustal plates may collide, move apart, or slide past each other.   Most volcanic activity and mountain building
occur at the boundaries of these plates, often resulting in earthquakes (and sometimes volcanoes).

Link to view plate boundaries on the Earth (where most earthquakes and volcanoes occur)

**  Folded, faulted (rock layers with breaks), tilted, and displaced rock layers show evidence of past crustal movement.
 
 

At the right (first a photograph showing an actual fault in a rock .. faults may be horizontal as well). At the far right a diagram of some different fault types.

Folds also provide evidence the Earth's crust is moving as the picture at the right shows.

Other evidence the Earth's crust has moved in the past is that the continents appear to fit together like puzzle parts
and fossils found in these parts which should fit together appear to correlate or match each other.

Fossils found in parts of the Adirondacks match those in Scandinavia (in Europe)!

This idea the continents have moved over time is called continental drift.