1. The Changing Environment
Guided Notes

2. The Changing Environment
Earth, the 3rd planet from the sun, is the only planet known to support life. Our planet has unique characteristics which are determined by its density, composition, and distance from the sun.
Some of these characteristics which enable earth to support life include the presence of liquid water, the composition of the layer of air surrounding the planet, and the presence of light and heat energy (coming from the sun).

3. The Changing Environment
Both the abundance of water and the atmosphere help to maintain Earth’s suitable range of temperatures (a range suitable for life).

4. The Changing Environment
Earth is composed of 3 general layers (collectively making the biosphere):
Lithosphere (layer of land that forms the earth’s surface)
Hydrosphere (all of the parts of the earth made of water)
Atmosphere (the layer of air the surrounds the earth)
All 3 layers are in constant motion and are comprised of more specific “layers” or divisions. All have also changed significantly since the birth of the earth, leading to the arrival & development of many living things.

5. Lithosphere
Lithosphere - Earth’s crust; varies in thickness from 10 to 70 kilometers. It rests on the molten mantle and is comprised of three general groups of rocks, depending on how they form.
Igneous rock forms when magma (molten rock in the mantle) reaches the surface (at this point called lava), cools, and solidifies (Granite, Basalt, etc…)

6. Lithosphere
Sedimentary rock forms when sediments accumulate (typically at the bottom of a body of water) and compress, becoming cemented (fossils are often found in these types of layered rocks, such as in Limestone…)
Metamorphic rock forms when pressure and heat over long periods of time transform igneous and sedimentary rocks into new types of rocks (Marble, Slate….)

7. Moving Earth
The crust is comprised of large, moveable tectonic plates, their movement a result of convection currents of heating and cooling magma in the mantle.
Interactions at plate boundaries can be of four types

8. Moving Earth
Sea floor spreading - new rock is pushing up and added to the edges of plates as they move away from each other
(ex: Mid-Atlantic Ridge, the largest geologic feature on earth)
Transform Fault - plates slide past each other,
Approximately 2 cm/year, typically in short bursts as friction creates tension… earthquakes common here…
San Andres in California

9. Moving Earth
Subduction - One plate slides under another; Volcanoes common here....
Example - Marianas Trench - 7 miles deep
Plate Collision - Two plates collide head on
Typically create mountain ranges (ex Himalayan mountains)

10. Special Situations
A special situation known as a “hot spot” under a plate creates island chains
Example - Hawaiian and Aleutian Islands), as a plate moves and the hot spot (which pushes up new land) does not...

11. Erosion
These activities of plates, along with weathering (breaking down rocks by water, wind, etc) and _____________ (weathered material is carried off), all together have resulted in the Earth’s present lithosphere condition, far ____________ than that of early earth.

12. Hydrosphere
2. Hydrosphere - Earth's waterways (mainly oceans….); have also changed in shape and location. Periods of global cooling (called ice ages) create huge masses of ice (Glaciers) which advanced from the poles and cover much of Earth's surface before eventually retreating.

13. Hydrosphere
There is evidence of at least 5 major periods in Earth’s history, the most recent having ended between 10,000 and 12,000 years ago. These heavy masses of ice scrape and gouge land (weathering!) as they move, depositing it elsewhere (Erosion), changing the face of the land. 5
10,000
12,000
Scrape & gouge
Weathering
Depositing
erosion

14. Examples
The Great Lakes, Cape Cod, and Hocking Hills are features resulting from the most recent ice age. The movements of crustal plates have also aided in the existence and disappearance of _________ in certain areas of the planet over time.

15. El Nino
El Nino - a recurring pattern of change in an ocean current - rather than the cold, nutrient rich water which normally flows northward up the coast of South America, each december warm, nutrient poor water flows southward for a few weeks. If this lasts for several months, warmer climate leads to flooding of agricultural areas and fishing activities decrease, depressing the economy.