September 5th, 2013

Students,

While I may have gotten off to a slow start today you guys rocked it! Today, we talked about forces of change, both external and internal.

Internal forces revolve around Plate Tectonics, the idea behind which is that the crust of the earth is made up of 11 different pieces that float on top of the molten layer of the earth called the Mantle. These pieces move and shift constantly colliding with each other, these collisions are the forces that we talked about.

Subduction (convergent) -  This is where two plates collide and the heavier plate gets swallowed up by the lighter plate and returns to the mantle. This recycles the crust (breaking the rock back down into magma) and has the potential to create mountains and volcanoes

Spreading (divergent) - This is where two tectonic plates move apart from each other. This type of movement occurs on the ocean floor. When the tectonic plates move apart magma rushes up and creates underground mountain ranges, or ridges.

Transformation - this is where two plates grind against each other. One of the primary examples of this type of movement is found in California along the San Andreas fault line. These two plates grind against each other creating several Earth Quakes that are experienced by the people of California, the quakes however have become a part of life with daily routines not being interrupted by minor quakes.

We also discussed External Forces that shape the earth.

Erosion - this is the wearing away and movement of sediments. This is cause by glaciers, wind, and water. The primary example that we talked about was the Colorado river grinding out the Grand Canyon over thousands of years.

Weathering - in the same line of Erosion we talked about weathering. The major differences between the two is the transportation aspect. In Weathering the object that is being changed doesn't really move, so large boulders with holes through them are prime examples of weathering.

Deposition- lastly we talked about deposition, this is where Rivers carrying sediments that they accumulate over their length, get deposited somewhere. One of the major places would be river deltas (where a river spreads thin when it reaches the ocean) The sediment creates a new land mass, that has very rich soil that is great for cultivation, which is why mankind has often flourished along rivers and river deltas.

Finally we talked about the "four-spheres" of the earth, Lithosphere (all land), Atmosphere (the air), the hydrosphere (the water), and the biosphere (all life). We drew pictures and wrote descriptions for each of these spheres and what they include.

Reminders: Unit 1 Test September 13th

Documents: http://imgur.com/a/zj1RT