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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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!!!

8. Plate system

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

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

20. 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

21. 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

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

23. Types of volcanoes

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