Post on 06-May-2015
GEOLOGY AND THE
ENVIRONMENT
The Walker School
Environmental Science
Earth’s Principal Systems
Atmosphere
Hydrosphere
Biosphere
Lithosphere
Magnetosphere
Cryosphere
Interaction Among Earth’s Systems
Table 1-1, p. 4
Earth is a Dynamic Planet
Geologic Hazards
Renewable Soil
Nonrenewable
Minerals
Energy Resources
Change is
the Norm
WHAT IS THE EARTH’S
STRUCTURE?
Earth’s Structure
The Moho, is the
boundary between the
Earth's crust and the
mantle. The Moho
serves to separate
both oceanic crust and
continental crust from
underlying mantle.
Seismic S & P Waves
Fig. 11-9b, p. 345
Seismic waves
provide evidence
that Earth’s internal
structure is layered,
not homogeneous.
Internal Processes
Convection Cells
Mantle Plumbs
(upwellings)
Plutonic Bodies
Plutonic Bodies
Fig. 4-24, p. 123
B: > 100 km2
S: <100 km2
L: inflated sills.
Internal Processes
Volcanic Bodies
External Processes
Mantle Plumbs and Interplate Hotspots
Fig. 2-22, p. 58
Mantle plumbs are
stationary, while the
plates move. This activity
has caused the creation
of new Hawaiian Islands
over the past 12 million
years.
Volcanic National Park, HIhttp://www.nps.gov/havo/
Fig. 5-3a, p. 137
Lava Tube in Hawaii
Most geographically isolated group of islands on
Earth; features include new cinder cones, glowing pit
craters, rivers of lava and fountains of spatter;
volcanic features at mass to the lithosphere, water to
the hydrosphere, carbon dioxide to the atmosphere,
and nutrients for plants.
WHAT IS PLATE
TECTONICS?
Earth’s crust is about 5% of it’s mass.
Earth has 15 Major Plates
Fig. 1-11, p. 17
Environmental Role of Plate Movement
Changes Climate
Stimulates Evolution
Changes Migratory
Patterns
Scope of the last Ice Age, 1200 BCE
Mantle (lithosphere)
Mantle (asthenosphere)
Ab
ys
sa
l p
lain
Mantle(lithosphere)
Oceanic crust
(lithosphere)
Abyssal
hills Abyssal
floor
Oceanic
ridge
Trench
Volcanoes
Folded mountain belt
Craton
Continental crust(lithosphere)
Continentalrise
Continentalslope
Continentalshelf
Abyssal plain
Abyssal
floor
Major Features of the Earth’s Crust
Convection from the Earth’s mantle rises and cools, driving the movement of the plates,
which in turn causes the folding of the lithosphere creating mountains and volcanoes.
Connections, Plates and Earth Systems
Table 1-3, p. 18
Convergent Plates
Fig. 2-18c, p. 53
Primarily responsible
for mountain building
events.
Continental Crust
Composed of many rock
types.
Can be as old as 4
billion years.
Varies in thickness from
20 to 80 km.
Makes up about 41% of
Earth’s surface.
Grand Teton National Park, WYhttp://www.nps.gov/grte
The Grand Tetons are one of the younger
mountain ranges on Earth. 24% of the Earth's
land mass is mountainous. 10% of people live
in mountainous regions. Most of the world's
rivers are fed from mountain sources, and
more than half of humanity depends on
mountains for water.A mountain is usually produced by the
movement of lithospheric plates,
called orogenic movement.
Mountain
Ice and snow
Altitude
Tundra (herbs,
lichens,
mosses)
Coniferous
Forest
Tropical
Forest
Deciduous
Forest
Tropical
Forest
Deciduous
Forest
Coniferous
Forest
Tundra (herbs,
lichens, mosses)
Polar ice
and snow
Latitude
Alpine Climate Zones
Divergent Plates
Builds new crust.
Atlanta Ocean is
getting bigger,
while the Pacific is
decreasing in size.
Mid-Atlantic Ridge & Iceland
One of the few places on earth that a
divergent pate is evident on land.
Divergent Plates Rift to Form Oceans
Fig. 2-15, p. 48
Rifting between the African
and Arabian Plate formed
the Red Sea.
Stages of Ocean
Basin Formation
Oceanic Crust
5 to 8 km thick.
Composed mainly of basalt and
gabbro.
Not older than 180 million
years.
Covered with dead organism
and sediment, about 1 km thick.
Little variability in composition.
Dunes Lagoon
SpitsStream
Glacier
Lake
Tidalflat
Barrierislands
Shallow marineenvironment
Volcanicisland
Coral reef
Abyssal plain
Deep-sea fan
Continental shelf
Continental slope
Continental rise
DeltaDunes
Beach
Shallow marineenvironment
Costal Features
WHAT GEOLOGIC PROCESSES
OCCUR ON THE EARTH’S SURFACE?
Weathering vs. Erosion
Weathering the decomposition of earth rocks, soils
and their minerals through direct contact with the
planet's atmosphere. Weathering occurs in situ, or
"with no movement", and thus should not to be
confused with erosion, which involves the movement
and disintegration of rocks and minerals by agents
such as water, ice, wind, and gravity.
Formation of the Grand Canyonhttp://www.youtube.com/watch?v=ktf73HNZZGY
Debris flows shown
in this clip erode
rock along the walls
of the canyon.
Arches National Parkhttp://www.nps.gov/arch/National
Fig. 6-CO, pp. 168-169
Erosion takes place
at different rates –
called differential
erosion
Produces: hoodoos,
spires, arches, and
pedestals
Hoodoos, Bryson Canyon National Parkhttp://www.nps.gov/brca/
Types of Weathering
Mechanical
Chemical
Biological
Fig. 6-1a, p. 170
Weathering of Granite
Physical Weathering
Mechanical or physical
weathering involves the
breakdown of rocks and
soils through direct
contact with atmospheric
conditions such as heat,
water, ice and pressure.
Badlands, SD
Chemical Weathering
Chemical weathering,
involves the direct effect
of atmospheric
chemicals, or
biologically produced
chemicals (also known as
biological weathering),
in the breakdown of
rocks, soils and minerals.
Lichens are part fungi
and part algae. They
derive their nutrients
from the rock and
contribute to chemical
weathering.
Biological Weathering from Plants
Fig. 6-6b, p. 174
Trees and other plants in
Lassen Volcanic National Park,
CA help break down parent
material into smaller pieces
and contribute to mechanical
weathering.
Salt Weathering (haloclasty)
Mechanical
Derives from an external source
(capillary rising ground water,
eolian origin, sea water along
rocky coasts, atmospheric pollution).
Favored by dry conditions in arid
climates.
The expanding salt crystals exert a
pressure on the walls of the rock
pores that exceeds the tensile
strength of the rock.
Marine Abrasion of Granite.
Isotasic Rebound
from Glaciers
Fig. 11-17, p. 351
Grosser Aletschgletscher, Switzerland
WHY DO EARTHQUAKES
OCCUR?
Earthquakes
Most occur along subduction zones and strike-slip
zones
Some occur in aseismic zones
Movement of magma causes tremors
Elastic Rebound Theory
Proposed by Henry F Reid in 1910
Rocks along a fault move relative to each other and
can bend elastically
Energy released from the bending causes shock
waves, which emanate from the plane of rupture
Liquefaction ofrecent sedimentscauses buildingsof sink
Landslides mayoccur onhilly ground
Shockwaves
Epicenter
Focus
Two adjoining platesmove laterally alongthe fault line
Earth movementscause flooding inlow-lying areas
HOW ARE EARTHQUAKES
MEASURED?
Measurements
Intensity
Amplitude
Duration
Scales
Richter Scale
Measurement of energy released for smaller and approximate earthquakes
Surface Wave Magnitude Scale
Measurement of energy released for extremely large earthquakes at a distance
Moment Magnitude Scale
Estimates the amount of displacement and area of rupture along the fault
Mercalli Scale
Directly describes the intensity of shaking rather than the magnitude
Useful in comparing damage from earthquakes at different locations
Seismographic Reading
Seismic Wave and Their Destructive Patterns.
Primary Modes of Destruction
Consolidation
Liquefaction
Vibration
Earthquake damage in a Afghan village.
Secondary Effects of Earthquakes
Rockslides
Urban Fires
Flooding
Tsunamis
Building Damage
Loss of Life
Canada
United States
No damage expected
Minimal damage
Moderate damage
Severe damage
Expected Damage From
Earthquakes
Indian Ocean Earthquakehttp://en.wikipedia.org/wiki/2004_tsunami
Tsunamis
A series of waves created when a body of water, such as an ocean, is rapidly displaced.
Earthquakes, mass movements above or below water, some volcanic eruptions and other underwater explosions, landslides, underwater earthquakes, large asteroid impacts and testing with nuclear weapons at sea all have the potential to generate a tsunami.
As the tsunami approaches the coast and the waters become shallow, the wave is compressed due to wave shoaling and its forward travel slows and its amplitude grows enormously, producing a distinctly visible wave.
Tsunami Warning System
WHAT ARE VOLCANOES?
Distribution of Volcanoes
Circum-Pacific
Belt (60%)
Mediterranean
Belt (20%)
Mid-Oceanic
Ridges (20%)
Fig. 5-20, p. 151
More common along both divergent than convergent plate boundaries.
Mainly composed of intrusive magma flows.
Composed of mafic magma that forms beneath spreading plates.
Pyroclastic materials are not common because lava is fluid.
Water pressure prevents gasses from expanding and escaping.
extinctvolcanoes
magmareservoir
centralvent
magmaconduit
Solidlithosphere
Upwellingmagma Partially molten
asthenosphere
General Structure
Crater Lake, OR Caldera
Caldera Floor of Crater Lake
Wizard Island, Crater Lake, OR
Learn About Megavolcanos Around the Worldhttp://www.pbs.org/wgbh/nova/megavolcano/about.html
VOLCANIC MONITORING
Important Monitoring Techniques
Fig. 5-23, p. 159
Fumarole Gas Monitoring
Chemically-selective sensors for SO2 and CO2 measure gas concentrations and a wind sensor measures wind speed and direction.
Data from solar-powered stations are transmitted to GOES geostationary satellite and then down to observatories every 10 minutes, providing near real time data on degassing of volcanoes
Ground Deformation Monitoring
Paint
Electronic Distance Meters
determine the horizontal movements that occur on active volcanoes
Tiltmeters
leveling surveys to measure vertical motions
Global Positioning Systems
allows us to measure horizontal motions much more accurately and conveniently, and also to estimate vertical motions in the same survey
Remote Sensing
The Advanced Very High Resolution Radiometer (AVHRR) is a space-borne sensor embarked on the NOAA family of polar orbiting platforms.
The primary purpose of these instruments is to monitor clouds and to measure the thermal emission (cooling) of the Earth.
The main difficulty associated with these investigations is to properly deal with the many limitations of these instruments, especially in the early period (sensor calibration, orbital drift, limited spectral and directional sampling, etc).
Primary Effects of Volcanoes
Pyroclastic Flows
Fumaroles
Landslides
Ash Fall
Earthquakes
High Temperatures
Secondary Effects of Explosions
Suffocation from Ash
Asphyxiation from
Volcanic Gasses
Tsunamis
Temperatures Decreases
Ash can coat your lungs, causing the
formation of a quick cement,
asphyxiating you.
Environmental Effects
Involved in the formation of continental crust and offset weathering and erosion
Provide nutrient rich soils
By trapping clouds at their peaks, water for agriculture
Agriculture based cultures are attracted to their bases
Volcanic soils in Sumatra.
Volcanic Gasses
Water Vapor
Carbon Dioxide
Nitrogen
Sulfur Dioxide
Hydrogen Sulfide
Carbon Monoxide
Hydrogen
Chlorine
Fig. 5-2, p. 136
Gasses emitted from fumaroles at the Sulfur Works in Lassen
Volcanic National Park, CA
Effects of Volcanoes on Climate
Nucleation, condensation, and sedimentation of aerosols (acid rain)
Change in Albedo from ash cloud
Tropospheric cooling from the addition of sulfur to the stratsophere
Ozone destruction through the formation of atomic chlorine
HYDROTHERMAL VENT
ECOLOGY
Hydrothermal Vents
Distributes heat and drives water circulation in the ocean through convection
Provides energy source in the form of hydrogen sulfide to benthic chemotrophs
Distributes minerals and influences the composition of the ocean
Hydrothermal Vent Ecosystem The chemosynthetic bacteria
grow into a thick mat which
attracts other organisms
such as amphipods and
copepods which graze upon
the bacteria directly. Larger
organisms such as snails,
shrimp, crabs, tube worms,
fish, and octopuses form a
food chain of predator and
prey relationships above
the primary consumers. The
main families of organisms
found around seafloor vents
are annelids,
pogonophorans,
gastropods, and
crustaceans, with large
bivalves, vestimentiferan
worms, and "eyeless" shrimp
making up the bulk of non-
microbial organisms.
Location of Major Vent Systems
Hydrothermal Vent Chemistry
Learn More About Ventshttp://www.divediscover.whoi.edu/vents/index.html