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

GEOLOGIC TIME SCALE Organizes Earth’s 4.6 billion years of history into subgroups Subgroups: Eons Eras Periods Epochs 4 Major Eons…

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

Ring of Fire Video (short)

Hot Spot (Short)

1. Transform Boundaries Plates slide past each other at transform faults Movement is horizontal (strike-slip fault) To the left- sinistral To the right- dextral 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

Plate tectonics 7 major plates, many smaller plates Moving relative to one another; average speed of a few inches per year 3 types of boundaries between plates: Convergent Divergent Transform-fault See http://www.scotese.com/pangeanim.htm

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.

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