Unit 1 “Physical & Chemical World” Earth Layers/Tectonics/Soils Atmosphere Water

Layers of Earth Core- center, mostly iron Inner core- 1220 km thick, T & P cause iron to solidify Outer core- 3480 km thick, liquid iron, creates magnetic field Mantle- 70% of earth’s interior, made of O, Si, Mg Asthenospere- closest to core, gelatinous, where magma is formed Upper mantle- cooler, more solid, brittle Crust- outermost layer Crust + upper mantle make up lithosphere

Plate Tectonics Tectonic plates- made of… Uppermost mantle Crust- 2 types: Oceanic- thin (5-10 km), dense, rich in Fe, Mg, Si, below sea level Continental- thick (20-70 km), less dense, rich in Ca, Na, K, Al Constantly moving about 1-10 cm/year 15 major plates- We are on North American Plate

Plate Boundaries Where 2 plates meet 3 types of plate boundaries “Ring of Fire” – Pacific Ocean

1. Transform Boundaries Plates slide past each other at transform faults Movement is horizontal (strike-slip fault) Mostly smooth movement If stuck, pressure builds, causes earthquakes

2. Convergent Boundaries 2 plates move toward each other 3 Types (next 3 slides)

a. OCEANIC - CONTINENTAL Oceanic plate is forced under continental plate Called subduction Creates deep-sea trench Creates volcanic mountains along continental plate. EX: Peru-Chile Trench and Andes Mountains of South America

b. OCEANIC - OCEANIC Oceanic plate is forced under another oceanic plate Called subduction Crust melts into mantle Creates deep-sea trench Creates arc of volcanic islands that parallel trench EX: Mariana Trench & Mariana Islands Aleutian Trench & Aleutian Islands

c.CONTINENTAL - CONTINENTAL Two continental plates collide Mountain ranges are created EX: Himalayas- Indian plate forced under Eurasian plate

3. Divergent Boundaries 2 plates move apart Creates rifts Magma comes to surface & cools, creating crust Usually in oceans, but can occur in continents (Africa’s Rift Valley) Creates mid-ocean ridges EX: Mid-Atlantic Ridge created when N.American plate pulls away from Eurasian plate.

CAUSES OF PLATE MOVEMENT Convection currents Hot mantle rises Cools down Cooled-down mantle sinks Creates currents that move plates.

THEORY OF CONTINENTAL DRIFT Alfred Wegner was first to propose theory of continental drift He said: All continents joined in large land mass called Pangea (Greek for “all land”) Pangea began breaking up 200 million years ago. Continents ended up where they are now Continents are still moving

Evidence of Continental Drift Fossils- similar plants & animals on widely separated continents Rock Formations- similar rock types & stratification between 2 continents Climate- Antarctica has coal deposits, indicating it had swamps, thus warmer weather= closer to equator

Earthquakes Epicenter- point where first movement occurs Damage depends on soil underneath Modern contractors build weak spots, pads/floats to absorb vibration Underwater earthquakes cause tsunamis Destroy coastal ecosystems Saltwater infiltrates soil sewage/industrial waste infect freshwater supplies

Tsunami December 2004 – Sumatran Tsunami

Volcanoes Good Created land (fertile soil), atmosphere, oceans Bad Release sulfur, combines with H20 to form sulfuric acid; interferes with solar radiation, cools climate (Mt. Pinatubo- Philippines) Dust/Ash- can change climate by blocking sunlight (1815- Mt. Tambora in Indonesia, snowed in July in parts of New England, “year without a summer”) Clouds of hot, toxic gases Mudslides

The Layered Earth Mantle Made of less dense materials Oxygen, magnesium, silicon Two regions: Lower mantle - solid Upper mantle or athenosphere - plastic and movable Convection currents form in the athenosphere and are responsible for plate tectonics

The Layered Earth Crust Also referred to as the lithosphere Composition is less dense than lower layers Skin of the physical planet Two types: Oceanic - higher density; basalts Continental - lower density; granites

Rock Types Rock Cycle - Cycle of creation, destruction, and metamorphosis. Three major rock classifications: Igneous Sedimentary Metamorphic

Igneous Rocks Most common type of rock in earth’s crust. Solidified from magma extruded onto the surface from volcanic vents. Quick cooling of magma produces fine-grained rocks. Basalt (makes up ocean floor) Slow cooling of magma produces coarse-grained rocks. Granite

Sedimentary Rock Formed by deposited materials that remain in place long enough, or are covered with enough material for compaction, may again become rock. Among the three major types of rock, fossils are most commonly found in sedimentary rock. Unlike most igneous and metamorphic rocks, sedimentary rocks form at temperatures and pressures that do not destroy fossil remnants.

Metamorphic Rock Pre-existing rocks modified by heat, pressure, and chemical agents. Chemical reactions can alter both the composition and structure of rocks as they are metamorphosed. Marble (from limestone) Quartzite (from sandstone) Slate (from mudstone and shale)

Weathering Mechanical - Physical break-up of rocks into smaller particles without a change in chemical composition. Chemical - Selective removal or alteration of specific components that leads to weakening and disintegration of rock. Oxidation Sedimentation - Deposition of loosened material.

Geological Boundaries

Effects of Agriculture on the Environment Chapter 12 Effects of Agriculture on the Environment

“Clean Water Farms” Case Study Intensive rotational grazing: is a system of grazing in which ruminant (animals that chew their cud) and non-ruminant herds are regularly and systematically moved to fresh pasture with the intent to maximize the quality and quantity of forage growth. The herds graze one portion of pasture, or a paddock, while allowing the others to recover. The grazers obtain the majority of their nutritional needs without the supplemental feed sources that are required in continuous grazing systems.

Many environmental problems result from agriculture: Soil erosion Sediment transport and deposition downstream On-site pollution from fertilizers and pesticides Deforestation Desertification Degradation of water aquifers Salinization Accumulation of toxic metals and organic compounds Loss of biodiversity

The American Dust Bowl of the 1930s Farming easily damages soils Intensive plowing and major drought loosened the soil The soil blew away during wind storms Houses, cars, and farms were destroyed Many farmers abandoned their farms The Grapes of Wrath was first a novel made into a popular movie about the dust bowl

Must Know This! Click Here for Info On Almost Every Birthday Cakes Rock! Click Here for Info

Soil Soil – complex mixture of weathered minerals materials from rocks, partially decomposed organic molecules, and a range of living organisms Not dirt! Soil is a living resource (“It’s alive!!!”), an ecosystem Approximately 20,000 different types of soils in the U.S. alone Building soil is a slow process!! It takes thousands of years to form 1 mm deep soil

Soil Composition and Texture 45% mineral Derived from parent material Underlying bedrock Deposition (i.e., glaciers, rivers, ocean currents, windstorms, landslides) Other 55% Air Water Organic matter from decomposition of organisms

Soil Composition and Texture Particle size is critical Larger particles = more pores of greater size Pores give soil drainage and aeration Loosely packed soils - good drainage and good aeration Tightly packed soils – bad drainage and poor aeration

Soil Composition and Texture Soil texture – the relative proportion of sand, silt, and clay in a soil sample Mineral composition Depending on a number of environmental factors, the soil can contain 0-100% OM Humus – brown, insoluble residue from the breakdown of organisms Provides nutrients Development of structure and texture (facilitates soil clumping, maintains spacing between soil particles)

Soil Particle Sizes Classification Size (mm) Gravel 2 – 64 Sand 0.05 – 2 Silt 0.002 – 0.05 Clay < 0.002

Soil Profiles Soils are stratified into horizontal layers called soil horizons. O Horizon (Organic layer) Leaf litter, partially decomposed organisms. Organic matter composition 20-30% Decomposition of organic material forming humus A Horizon (Topsoil) Mineral particles mixed with organic material. Most root activity Most biological productive zone Typically has a dark color (OM) Referred to as topsoil

Soil Profiles E Horizon (Leaching Zone) Soil horizons diagram E Horizon (Leaching Zone) Not present in all areas…In acidic soils Depleted of soluble nutrients. Weak organic acids typically dissolve and remove silicate clay, aluminum, and iron Lighter color than A or B horizons B Horizon (Zone of Accumulation) Often dense texture from accumulating nutrients. Well-developed examples are bright in color C Horizon (Parent Material) Least weathered rock fragments with little organic material.

Soil Texture Triangle WATCH VIDEO!

Soil profile

Global Soil Degradation

If you need a refresher on soil or missed class…watch this video! Click here!

Where Eroded Soil Goes: Sediments Also Cause Environmental Problems Lots of soil is in water runoff that ends up in streams & rivers and then deposits it at the mouths of the rivers. These deposits end of destroying some fisheries Coral reefs are also being destroyed by sediments landing on them Watch Video Here