CHAPTER 2—the Dynamic Earth Objectives Describe the origins of earth Identify and describe earths 3 major parts Describe various nutrient cycles Define weather and climate Explain short and long term changes that happen on earth

2.1 The Earth Forms Earthed formed about 4.6 b.y.a The earth is solid (not gaseous) and is composed of 3 main layers: Crust—solid continental plates made of rock and soil. Lighter crust forms the continents Heavier crust forms the ocean floors Crust is broken into plates that move

2.1 The Earth Forms Below the crust is the Mantle The Core Made of molten (liquid) rock There seem to be ‘hot spots’ in the mantle Ex. Hawaii, Yellowstone The Core Solid outer core Liquid inner core The core is made of Iron and causes the earth’s magnetic fields.

2.1 The Earth Forms Atmospheric beginnings As the earth cooled, gases and vapors erupted and became the beginnings of the oceans and the atmosphere. Meteors and comets battered the earth’s surface. The environment was still not very conducive to life. Still, tiny living things appeared on earth ~3.5 b.y.a. Similar to today’s extremophyles. Could withstand the conditions How did this happen?? (discuss)

2.1 The Earth Forms About 2.7 b.y.a.—life forms appear that begin to change the planet Cyanobacteria (blue-green algae) develop photosynthetic capabilities. Oxygen becomes more prevalent in the atmosphere Methane and Ammonia are removed from the atmosphere Earth can then support a variety of different life forms.

2.2 Land, Water, Air Objectives Describe effects of plate movement Identify the main parts of the hydrospere Identify the parts of the atmosphere Describe benefits of the atmosphere

2.2 Land, Water, Air Lithosphere—the land Hydrosphere—the water Earth’s biosphere—where living things exist Lithosphere—the land Hydrosphere—the water Atmosphere—the air

2.2 Land, Water, Air LITHOSPHERE Outer surface of the earth is covered by plates. Continents Ocean floor Plate Tectonics—explains the mechanisms that cause the earth’s crust to move. Volcanos Rift valleys Mountains Continental Drift—theory that describes the movements of the plates

2.2 Land, Water, Air Tsumani of Dec. 26, 2004 here Mount Saint Helens here

2.2 Land, Water, Air HYDROSPHERE Water layer of the earth Oceans Lakes Streams Ground water Water vapor Water is necessary to life Aids in chemical reactions Absorbs and holds (helps maintain a constant temp.)

2.2 Land, Water, Air ATMOSPHERE—has 4 main layers Troposphere—(0-16 km) Where animals can live Where weather occurs Stratosphere—(16-50 km) Ozone layer Protects troposphere from UV rays Mesosphere—(50-80 km) Thermosphere—(80-480 km) Has a layer of high temperature within it Generally, as one increases elevation, temperature decreases

2.2 Land, Water, Air Will reflect some of the sun’s energy to prevent over heating (2000 F without it) Will retain some heat to prevent too much cooling (-200 o F without it)

2.3 cycles Your brochures are due today.

2.4 Climate and Weather Weather: What’s happening at the moment Climate: long-term averages of weather conditions

2.4 Climate and Weather What affects climate? Latitude—distance away from the equator Tropics, temperate and polar zones Tilt of the earth (23.5o) Results in seasons—solstice and equinox Rotation of the earth Coriolis effect – winds Trade winds, prevailing westerlies, arctic easterlies. Physical features Mountains, oceans, lakes

Where are deserts? Most deserts lie along the Tropic of Cancer and the Tropic of Capricorn.  In desert regions, dry air currents blow across the land.  These dry air currents can blow hot or cold but they rarely carry rainclouds. 

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2.5 Changing Earth Continental Drift Erosion—wind, water. Theory is that land masses move over geological time Pangea—super continent that broke apart Drift results in mountains, rifts Erosion—wind, water. Global Climate Change Earth’s average surface temperature cycles Humans have lived in a mild part of that cycle

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