How does the Earth change over time? Geological Processes How does the Earth change over time?

Lithosphere (crust and upper most solid mantle) Structure of the Earth Mantle Core Crust Low-velocity zone Solid Outer core (liquid) Inner core (solid) 35 km (21 mi.) avg., 1,200˚C 2,900km (1,800 mi.) 3,700˚C 5,200 km (3,100 mi.), 4,300˚C 10 to 65km 100 km 200 km 100 km (60 mi.) 200 km (120 mi.) Lithosphere (crust and upper most solid mantle) Asthenosphere Fig. 10.2, p. 212

Zones of earth’s structure Core – solid Mantle – thick solid zone Asthenosphere – under the rigid outermost part of the mantle – hot, partly melted rock that flows like plastic Crust – outermost and thinnest zone Contains: CONTINENTAL CRUST - lies under continents and continental shelf OCEANIC CRUST – under ocean basins and covers 71% of earth’s surface

Composition of Earth’s Crust Oxygen 46.6% Silicon 27.7% All others 1.5% Magnesium 2.1% Potassium 2.6% Sodium 2.8% Calcium 3.6% Iron 5.0% Aluminum 8.1% Fig. 10.4, p. 213

Mantle (asthenosphere) Features of the Crust Oceanic crust (lithosphere) Abyssal hills floor Oceanic ridge Trench Volcanoes Folded mountain belt Craton (very stable) Mantle (lithosphere) Mantle (asthenosphere) Abyssal plain Continental crust Mantle Continental rise slope shelf

Internal Earth Processes Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary Trench Volcanic island arc Rising magma Subduction zone Trench and volcanic island arc at a convergent plate boundary Fracture zone Transform fault Transform fault connecting two divergent plate boundaries Internal Earth Processes CONSTANT CHANGES INTERNAL PROCESSES – build up the planet’s surface Energy provided from heat in the interior Causes the mantle to deform and flow Two kinds of movements: CONVECTION CURRENTS MANTLE PLUMES – mantle flows upward in a column

Plate Tectonics Movement of rigid plates called TECTONIC PLATES caused by convection currents and mantle plumes Plates are 60 miles thick and are made up of continental and oceanic crust – called the LITHOSPHERE Plates are constantly moving on the asthenosphere at different speeds Concept accepted in early 1960’s was called continental drift theory Now called PLATE TECTONICS PRODUCES: VOLCANOES and EARTHQUAKES – found at plate boundaries OCEANIC RIDGE SYSTEM TRENCHES Helps explain patterns of biological evolution!!!

Plate system

TYPES OF BOUNDARIES Mid-Atlantic Ridge system DIVERGENT PLATE (Constructive Plate) BOUNDARIES - plates move in opposite directions Builds up the earth’s crust Mid-Atlantic Ridge system

TYPES OF BOUNDARIES CONVERGENT PLATE– plates are pushed together by internal forces Oceanic lithosphere is sub-ducted under the continental at subduction zones Trenches normally form at the boundary

Types of Boundaries Transform faults – occur when plates slide past one another along a fracture (fault) in the lithosphere Most are on the ocean floor

External Geologic Processes Based directly or indirectly on energy from the sun and gravity (tend to wear down the earth’s surface) Two types: EROSION - material is dissolved, loosened, or worn away at one part of the earth’s surface and deposited somewhere else (Caused by wind, water, and human activities). WEATHERING – produces loosened material that can be eroded MECHANICAL – large rock fragments broken into smaller pieces (One type called FROST WEDGING- caused by freezing, expansion, and splitting of rock) CHEMICAL – chemical reactions decompose a mass of rock mainly reacts with oxygen, carbon dioxide, and water in the atmosphere and ground

Minerals and rocks Mineral Either an ELEMENT or INORGANIC COMPOUND – naturally occurring and a solid Some are single elements – Au, Ag, most are compounds – mica, salt, quartz Rock Any material that makes up a large natural continuous part of the earth’s crust Can contain only one mineral but most consist of two or more minerals Example: GRANITE – quartz, mica, and feldspar FORMS FROM MOLTEN ROCK MATERIAL (MAGMA) Wells up from upper mantle or deep crust, cools, hardens into rock – EXAMPLE: GRANITE Igneous Rock FORMS FROM LAVA Forms above ground when magma cools Main part of earth’s crust Source of many nonfuel mineral resources

The Rock Cycle Sedimentary Rock Deposition Shale, Sandstone, Transport Igneous Rock Granite, Pumice, Basalt Sedimentary Rock Shale, Sandstone, Limestone Metamorphic Rock Slate, Quartzite, Marble Magma (Molten Rock) Weathering Erosion Transport Deposition External Processes Internal Processes Heat, Pressure Fig. 10.8, p. 217

Natural Hazards: Earthquakes Caused by stress in crust which deforms rock until it fractures producing faults. This faulting or abrupt movement causes EARTHQUAKES Energy is released as shock waves which move outward Focus - point of initial movement Epicenter – point on earth’s surface above the focus Magnitude – measures severity of earthquake Richter scale-measured on a seismograph Ranked as: Insignificant – less than 4 Minor (4.0 – 4.9) Damaging (5.0 – 5.9) Destructive (6.0 – 6.9) Major (7.0 – 7.9) Great (over 8.0) *Amplitude for each is 10 x greater than the next smaller unit

MORE … AFTERSHOCKS– smaller earthquakes that follow – often over a period of months FORESHOCKS – seconds to weeks before the main shock PRIMARY EFFECTS - shaking, sometimes permanent vertical or horizontal displacement of earth SECONDARY EFFECTS - rock slides, fires, flooding, tsumanis

Earthquakes Two adjoining plates move laterally along the fault line Liquefaction of recent sediments causes buildings of sink Landslides may occur on hilly ground Shock waves Epicenter Focus Two adjoining plates move laterally along the fault line Earth movements Cause flooding in Low-lying areas

Expected Earthquake Damage Canada United States No damage expected Minimal damage Moderate damage Severe damage

REDUCING EARTHQUAKE DAMAGE EXAMINE HISTORICAL RECORDS AND MAKE GEOLOGICAL MEASUREMENT MAP HIGH RISK AREAS ESTABLISH BUILDING CODES TRY TO PREDICT WHERE AND WHEN EARTHQUAKES WILL OCCUR

Natural Hazards: Volcanoes MAGMA REACHES THE EARTH’S SURFACE THROUGH A VENT OR CRACK RELEASES: EJECTA – CHUNKS THROUGH ASH LIQUID LAVA GASES – water vapor, carbon dioxide, sulfur dioxide USUALLY FOUND IN SAME AREAS AS EARTHQUAKE ACTIVITY BENEFITS: FORM MOUNTAINS, LAKES, ISLANDS, AND PRODUCE FERTILE SOILS AS LAVA WEATHERS

Volcanic Eruptions extinct volcanoes central vent magma reservoir conduit Solid lithosphere Upwelling Partially molten asthenosphere

Types of volcanoes

REDUCE VOLCANIC HAZARDS LAND – USE PLANNING BETTER PREDICTION EFFECTIVE EVACUATION PLANS