PowerPoint Presentation€¦ · Normal Polarity= rocks magnetic field points north (classified...
Transcript of PowerPoint Presentation€¦ · Normal Polarity= rocks magnetic field points north (classified...
14-1 What Are the Earth’s Major
Geological Processes and Hazards?• Concept 14-1A Gigantic plates in the
earth’s crust move very slowly atop the
planet’s mantle, and wind and water move
the matter from place to place across the
earth’s surface.
• Concept 14-1B Natural geological
hazards such as earthquakes, tsunamis,
volcanoes, and landslides can cause
considerable damage.
• 3rd Planet from sun
• Formed ~4.6 billion years ago
• Shape = oblate sphere
Caused by Earth’s rotation
• Difference between tallest
mountain and deepest ocean
trench is ~20 km
40,007 km around
40,074 km around
3 major concentric zones of earth’s interior
Crust (Continental and Oceanic-71%)
Mantle
Core
Structural zones of earth’s interior
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner core
Earth’s Interior
Major Features of the Earth’s
Crust and Upper Mantle
Plate Tectonics
Alfred Wegener’s
Hypothesis
Continental Drift: Hypothesis that the
continents once formed part of a single
landmass called a supercontinent
Began breaking up ~250 million years ago
Continents drifted to present location
Evidence of Continental Drift
Fossil Evidence
Fossils found of same species in areas where
continents were once connected
Evidence from Rock Formations
Ages and types of coastal region rocks matched
closely
Climatic Evidence
Glacier deposits where climates are warm
Mid-Ocean RidgesMid-Atlantic Ridge mapped out in 1947
Mid-ocean ridges: undersea mountain ranges through the center of which run steep, narrow valleys.
Ridge Facts
The sediment covering the sea floor is thinner closer to a ridge
Younger sediment closer to a ridge
Rocks on land ~3.8 billion years
Rocks on sea floor < 175 million years old
Magma
Oceanic
Crust
Sea-Floor SpreadingHess proposed a rift (crack at
center of ridge) that magma
flowed from, ocean floor
spreads, magma cools
forming rock and replacing
gap in ocean floor
Dietz defined this process
Sea-floor Spreading
PaleomagnetismStudy of the magnetic properties of rocks
Magnetic ReversalsNormal Polarity= rocks magnetic field points north
(classified together in same time period)
Reverse Polarity= rocks magnetic field points south
(classified together in same time period)
Magnetic SymmetryStripped magnetic pattern same on each side of the ridge
Magnetic patterns help date ocean floor and support sea-
floor spreading
Plate tectonics is the
theory that explains
why and how
continents move and
is the study of the
formation of features
in Earth’s crust
How Continents Move Lithosphere is divided into tectonic plates, which can also include continental crust, oceanic crust, or both
Asthenosphere is under great pressure, therefore flows (moves) slowly allowing the tectonic plates to move above it
Tectonic PlatesAbout 7-8 Major Plates (+7-8 more
minor plates)
Primarily identified using earthquake
data
Frequent earthquakes is evidence of a
boundary
Volcanoes are also an identifier when
they form from magma generated
during plate motion
The Earth’s Major Tectonic Plates
Types of Plate Boundaries
The San
Andreas Fault
as It Crosses
Part of the
Carrizo Plain
in California,
U.S.
Causes of Plate Motion
Mantle Convection
Ridge PushThe asthenosphere exerting force on the plate
pushing the plate away from the ridge
Slab PullThe force exerted
by the sinking plate
Direction of plate motion
Sinking due to densityResulting plate motion
Resulting plate motion
Sinking lithosphere
Moving asthenosphere
Rifting and Continental ReductionRifting: the process by which a
continent breaks apart
Rifts form because heat builds up
under the insulating continent, the
lithosphere becomes thinner (weaker),
the continent breaks apart at the
weakness
Terranes and Continental Growth
Terrane: A piece of lithosphere that has
a unique geologic history that differs from
the histories of the surrounding lithosphere
3 Characteristics:
1.Rocks and Fossils differ between terranes
2.Major faults at terrane boundaries
3.Magnetic properties differ between terranes
AccretionThe process in which a terrane becomes part of a continent
Occurs at Convergent Boundaries
http://www.classzone.com/
books/earth_science/terc/
content/visualizations/es0
808/es0808page01.cfm?c
hapter_no=visualization
Effects of Continental Change
Changes in ClimateLarge continent mass was located near the South
Pole so was covered by ice
When continents moved toward equator the ice
melted
Changes in LifeRifts and Mountains separate species
Species evolve differently when separated and
new species may emerge
Supercontinent Cycle
Some Parts of the Earth’s Surface
Build Up and Some Wear Down
Internal geologic processes
- Generally build up the earth’s surface
External geologic processes
– Weathering• Physical, Chemical, and Biological
– Erosion• Wind
• Flowing water
• Human activities
• Glaciers
Weathering: Biological,
Chemical, and Physical
*SEE WEATHERING
AND EROSION
POWERPOINT!
Volcanoes Release Molten Rock
from the Earth’s Interior
• Volcano
– Fissure: Central vent or long crack
– Magma: Partially molten asthenosphere
– Lava: Magma that reaches the earth’s
surface
• Benefits of volcanic activity
– Scenery
– Fertile soil produced by weathering of lava
May 18, 1980 Eruption of
Mount St. Helens• Elevation of summit: 9,677 feet
before; 8,363 feet after;
• Magnitude 5.1 earthquake at 8:32 a.m.
• Fatalities
– Human: 57
– Wildlife: Countless non-burrowing wildlife in blast
area, including about 7,000 big game animals;
about 12 million salmon fingerlings in hatcheries
1991 Eruption
of Mount
Pinatubo,
Philippines
• Eruption was Forecasted!
– Resulted in the saving of at least 5,000 lives
and at least $250 million in property
– However, a few jets flying far to the west of the
Philippines encountered ash and sustained
about $100 million in damage
Creation of a Volcano
Earthquakes Are Geological
Rock-and-Roll Events• Earthquake
– Seismic waves: form of energy vibrations
– Focus: location where earthquake begins BELOW the surface
– Epicenter: location ABOVE the surface over focus
– Magnitude: measure of ground motion
– Amplitude: size of the seismic wave
Richter Scale• Developed in 1935 by Charles F. Richter
– California Institute of Technology
– Magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.
• Richter scale – Insignificant: <4.0
– Minor: 4.0–4.9
– Damaging: 5.0–5.9
– Destructive: 6.0–6.9
– Major: 7.0–7.9
– Great: >8.0
Earthquakes Are Geological
Rock-and-Roll Events• Foreshocks: occurs from seconds to
weeks BEFORE the main shock
• Aftershocks: occurs months after main
shock, but will decrease in frequency
over time
Major Features and Effects of
an Earthquake
Areas of Greatest Earthquake Risk in
the United States
Areas of Greatest Earthquake Risk
in the World
1995, Kobe (Japan)
• The 1995 Great Hanshin
Earthquake (M=6.9), commonly
referred to as the Kobe
earthquake, was one of the
most devastating earthquakes
ever to hit Japan.
• More than 5,500 were killed
and over 26,000 injured.
• The economic loss has been
estimated at about $US 200
billion.
The San Francisco earthquake in 1989 killed nine
people and injured hundreds.
The earthquake was measured to be a 6.9
Which caused collapsed bridges and freeways,
fires, shattered buildings, gaping cracks in roads
and land slides
San Francisco earthquake
1989 earthquake in san Francisco caused a lot
of damage to the city
Earthquakes on the Ocean Floor Can
Cause Huge Waves Called Tsunamis
• Tsunami (tidal wave): series of large waves
generated when ocean floor suddenly rises or drops
• Detection of tsunamis: ocean buoys, pressure
recorder (data relayed to weather buoy)
December 2004: Indian Ocean tsunami
• Magnitude of 9.15
• Waves height: 31 meters (100 feet)
• 228,000 people died
• Role of coral reefs and mangrove forests
in reducing death toll
– Sri Lanka-illegal coral mining and reef
damage were factors in causing the greatest
damage here
Formation of a Tsunami and Map of
Affected Area of Dec 2004 Tsunami
Shore near Gleebruk in Indonesia
before and after the Tsunami on
June 23, 2004
Gravity and Earthquakes Can
Cause Landslides• Mass wasting
– Slow movement
– Fast movement
• Rockslides
• Avalanches
• Mudslides
• Effect of human activities on such
geological events
– Forest clearing, road building, crop growing
California PCH and Malibu
How Are the Earth’s Rocks Recycled?
• Concept 14-2 The three major types of
rocks found in the earth’s crust—
sedimentary, igneous, and metamorphic—
are recycled very slowly by the process of
erosion, melting, and metamorphism.
Three Major Types of Rocks
Earth’s crust
• Composed of minerals and rocks
Three broad classes of rocks, based on
formation
1. Sedimentary formed by the lithification of weathered
rock debris that has been physically transported and
deposited
• Sandstone
• Shale
• Dolomite
• Limestone
• Lignite
Three Major Types of Rocks
2. Igneous: formed by the cooling and
solidification of molten magma
• Granite
• Lava rock
3. Metamorphic: alteration of existing rocks by either excessive heat and pressure, or through the chemical action of fluids.• Anthracite
• Slate
• Marble
Natural Capital: The Rock Cycle Is the
Slowest of the Earth’s Cyclic Processes
4 Characteristics of Minerals
1. It is INORGANIC
2. It OCCURS NATURALLY
3. It is a CRYSTALLINE SOLID
4. It has CONSISTENT CHEMICAL
COMPOSTION
Silicate Minerals
Minerals that contain a combination
of silicon and oxygen
Make up 96% of Earth’s crust
Feldspars are the most common
silicates
Silicate Minerals
Chemical CompositionKalSi308 – Potassium
Aluminum Silicate
Color
Typically off-white or
shades of red, orange
and brown, occasionally
green.
Cleavage
One perfect cleavage
and one good cleavage
that meet at nearly 90°
Hardness 6 (harder than glass)
Specific Gravity 2.6
Luster
Crystals are vitreous
(glass-like) to
porcelaneous (porcelain-
like)
Streak white
Potassium Feldspar
Nonsilicate Minerals
Do not contain silicone-oxygen
compounds
~ 4% of Earth’s Crust
1. Carbonates
2. Halides
3. Native elements
4. Oxides
5. Sulfates
6. Sulfides
Nonsilicate Minerals
PyriteAKA
“Fools Gold”
Crystalline Structure of silicates
Crystalline Structure of nonsilicates
Examples include cubes,
hexagonal prisms, and
irregular masses
Identifying using Physical
Properties
• Color
• Streak
• Luster
• Cleavage and
Fracture
• Hardness
• Crystal Shape
• Density
There Are Several Ways to
Remove Mineral Deposits• Surface mining
– Shallow deposits removed
• Subsurface mining
– Deep deposits removed
• Type of surface mining used depends on
– Resource
– Local topography
There Are Several Ways to
Remove Mineral DepositsTypes of surface mining
– Open-pit mining: digging holes to remove ores
(e.g. iron, copper, gold) and sand, gravel, or stone
– Strip mining: extract minerals on surface in
large horizontal beds
– Contour mining: cutting terraces into side of
hill or mountain
– Mountaintop removal: remove entire top of
mountain
Natural Capital Degradation: Open-
Pit Mine in Western Australia
Natural Capital Degradation: Contour Strip
Mining Used in Hilly or Mountainous Region
Natural Capital Degradation: Mountaintop
Coal Mining in West Virginia, U.S.
Mining Has Harmful
Environmental Effects• Scarring and disruption of the land surface
– E.g., spoils banks (a series of hills left behind
from area strip mining)
• Loss of rivers and streams
• Subsidence: the collapse of land above
some underground mines
Mining Has Harmful Environmental Effects
• Major pollution of water and air
– Acid mine drainage: rainwater seeps through
mine and carries H2SO4 to groundwater
• Effect on aquatic life
– EPA says 40% of watersheds in US are
polluted
• Large amounts of solid waste
– 75% of all US solid waste
Banks of Waste or Spoils Created by Coal
Area Strip Mining in Colorado, U.S.
Illegal Gold Mine
Ecological Restoration of a Mining
Site in New Jersey, U.S.