GEOL 102 - Exam 2

Landslides occur on...

unstable slopes

____ ____ is usually related to the steepness of the slope and the type of material present.

Slope stability

Angle of repose

the steepest angle at which loose material will not slide down slope

Angle of repose for Fine Sand

35 degrees

Angle of repose for Coarse Sand

40 degrees

Angle of repose for Angular Pebbles

45 degrees

More Cohesive Sand

Damp Sand

Least Cohesive Sand

Water-saturated Sand

Moderately Cohesive Sand

Dry Sand

Vegetation adds...

stability

Landslides are a part of a process called ____ _______

Mass Wasting

Mass Wasting

Any down-slope movement of soil or rock under the influence of gravity:

-Landslides

-Debris flows

-Soil creep

-Rockfalls

Deadly killers

Billions in property damage

Type of material in Mass Movements

Rock

Soil

How materials move during Mass Movements

Sliding

Flowing

Falling

How fast the material moves

Slide planes: discreet failure surfaces

Landslide: Slump

Most common kind of landslide

Spoon-shaped

Move about a center of rotation

Grow headward

Encouraged by cutting at the toe

Block glide

Blocks of land slide down together

Rock Avalanche

Flows

Water and air help these landslides move

Earth Flow

Rain soaked land flows down

Debris Flow

Creep

Slow (mm/year) movement downslope on steep slopes

Freeze/thaw

Wet/dry

Burrowing animals

Tree falls

Soil

-Produces food for humans

-Produces trees for lumber and paper

-Supports nearly all life

-Carrying capacity of planet depends on availability and productivity of soil

On average, it takes _____ years to make an inch of soil.

several hundred (about 500)

What is soil made of?

25% - Water

25% - Gases

45% - Mineral Matter

5% - Organic

Soil changes with...

depth

O Horizon

organic material

A Horizon

Rainwater and roots are active; soil aggregation

B Horizon

Zone of accumulation

C Horizon

Rotten rock layer, rocks break down chemically and material behaves like soil still.

Soil is a product of...

weathering

Weathering

-Breakdown of rocks and minerals at and near the Earth's surface

-Physical disintegration

-Chemical decomposition

Water takes advantage of...

pre-existing fractures

in rocks

Water expands by ___% when it freezes

9

_____ is an important factor in chemical weathering

time

The type of _______ also affects the rate of chemical weathering

bedrock

Effects of Plowing

• Exposes soil to physical erosion

• Exposes organic matter to decomposition

(Some organic matter is bound by minerals that protect it from microbial decomposition. Plowing releases this, for decomposition and oxidation)

Benefits of soil

Food

Habitats

Ecosystems

Drought, extensive plowing, and high winds cause...

dust storms

Soil Loss

Huge areas have lost most productive soil

Eroded soil becomes sediment in streams

Soil loss by size

• one third of U.S. topsoil lost so far

• globally, lost area size of China and India

Eroded soil deposits sediment in streams, creating...

• muddies rivers

• fills reservoirs

• disrupts coastal zone

Soil Conservation

No-till agriculture

An agricultural method in which farmers do not turn the soil between seasons, used as a means of reducing erosion

"Organic" farming

Conserve soil biological activity, minimize off-farm inputs of materials and energy, forbid herbicides, pesticides, genetically modified crops or feed stocks, avoid hormones, antibiotics, and other drugs, allow animals to be outside for part of their lives, and many other "rules."

Biogeochemical Cycles

A biogeochemical cycle is the complete path a chemical takes through the four major components of Earth's system

Carbon Cycle

The organic circulation of carbon from the atmosphere into organisms and back again

Carbon Budget

the overall exchange of carbon between the different systems on Earth. It should naturally remain balanced as carbon moves between sources and sinks.

Tropical Deforestation (per year)

13 Million Hectares

Percentage of water in ocean and salt lakes

97.41%

Percentage of water in ice and snow

1.984%

Percentage of water in groundwater

0.592%

Percentage of water in lakes and rivers

0.0071%

Percentage of water in soils, wetlands, and biota

0.0059%

Percentage of water in the atmosphere

0.001%

Freshwater is brought to us

by _______

the water cycle

Water Cycle

-Precipitation

-Runoff

-Groundwater recharge

-Evaporation

-Evapotranspiration

---Evaporation of water

---Transpiration from plant leaves

Precipitation

Any form of water that falls from clouds and reaches Earth's surface.

Runoff

Water that flows over the ground surface rather than soaking into the ground

Groundwater recharge

A process by which water percolates through the soil and works its way into an aquifer.

Evaporation

Liquid to gas

Evapotranspiration

The evaporation of water from soil plus the transpiration of water from plants.

Most fresh water is...

groundwater

Ground water

-Most in pore spaces and fractures

-Hydrogeologists are better than dowsers at locating sites for wells

-40% of public water supplies

-Important for irrigation

Helps maintain streamflows

Zone of saturation

The lower zone where water accumilates between small rock particles.

Zone of aeration

The upper zone which usually isn't completely filled with water, but with rocks and soil too. ( Is about Ground water)

Pore space

The space between soil particles

Infiltration ground water

Aquifer

water quantity sufficient for springs and wells

Porosity

percentage of openings to total volume of rock

Permeability

ease with which fluids flow through an aquifer

Hydraulic conductivity

more precise term for flow through an aquifer

Perched water table

an isolated zone of saturation above the rest of the local water table

Capillary fringe

The area just above the water table, in the zone of aeration, where water moves upward from the water table by capillary action.

Aquiclude

A body of rock that will absorb water slowly, but will not transmit it fast enough to supply a well.

"Confined" aquifer

A groundwater storage area trapped between two impermeable layers of rock.

Streams and springs are influenced by...

groundwater

Losing stream

- above local water table

- can create a recharge mound

Gaining stream

Intersects water table and is fed in part by groundwater

Cone of depression

lowering of the water table around a pumping well

Mining groundwater

can cause shallow wells to go dry

High Plains aquifer

- Ogallala Sandstone

- Large overdrafts

- Government subsidies favor water-loving corn

- By 2020, 1/4 of water will have been mined

The shrinking Aral Sea

- Once fourth-largest lake in the world

- Soviet Union diverted rivers for irrigation (evaporation exceeds inflow)

- Blowing dust from dry lake-bed causes air pollution

Pollution

introduction of harmful materials or conditions to environment

Contamination

rendering something unusable due to pollution

Toxic

materials that are harmful to humans and other organisms

Carcinogen

cancer-causing agent

Point Source

a specific locality at which pollutants enter the environment

Non-point Source

emission from diffuse or broad area-based sources

Measurements for concentrations

micrograms/cc, milligrams/cc, ppm, ppb, etc.

Physical hazards

• Earthquakes

• Tsunamis

• Storms

• Floods

• UV radiation

• Volcanoes

Chemical hazards

Metals (Mercury, Chromium, Lead, Arsenic)

Herbicides/Insecticides (Dioxin, others)

Fertilizers

Petroleum

products/solvents

Endocrine disruptors

( DDT, PBCs, BPA?)

Ozone

Lead

impairs neurological function

Arsenic

Arsenic occurs in groundwater-

Variable spatially

Natural sources?

Concentrated in some regions?

Why?

Hormonally Active Agents (HAAs)

transmit information in addition to that provided by natural hormones to control DNA formation in cells.

Amphibians are particularly vulnerable to DDT and other pesticides

Tropospheric Ozone

a powerful oxidant

Leads to respiratory problems (asthma, etc.), and

disrupts plant cells as well!

Asbestos

Fibrous mineral (Chrysotile) used for insulation

- carcinogenic when inhaled

Electromagnetic Fields

Concerns regarding radio-frequency radiation and health.

Effective dosage

ED-50 Does something (beneficial) for 50% of people

Toxic dosage

TD-50 Is toxic for 50% or people

Threshold Dose: Level below which there is no effect (could be 0)