Earth Science Exam #3

Which statement best describes science?

Science is the process of discovery

Which of the following is not a characteristic of scientific explanations

They are able to answer all questions

Scientific results are unpredictable and are mainly determined by the personal views of the scientists.

False

Once a scientific explanation has been established it never needs to be changed

False

What distinguishes science from non-science?

Science is based on empirical observations

Which type of plate motion is characteristic of a convergent boundary?

Plates move toward one another

Which type of plate motion is characteristic of a divergent boundary?

Plates move away from one another

Which type of plate motion is characteristic of a transform boundary?

Plates move past one another

What is the proper order of Earth's compositional layers from the interior to the surface?

Core, mantle, crust

At least three seismograph stations from three different locations are required to determine the epicenter of an earthquake

True

A Richter magnitude 6 earthquake has about double the ground motion compared to a Richter magnitude 5 earthquake

False

A magnitude 8.0 earthquake will always cause more damage and loss of human life than a magnitude 7.0 earthquake

False

P and S waves are both body waves

True

Magnitude is a measure of the size of an earthquake while intensity deals with the earthquake's effect on humans

True

This earthquake-generated hazard can occur when seismic waves shake saturated soils

Liquefaction

What is the difference between earthquake magnitude and intensity?

Magnitude measures earthquake size, intensity documents damage

Which volcanoes are most likely to explode and why?

Strato- because the magma is more viscous than in shield volcanoes

Shield volcano

Broad gentle slopes, low viscosity (basalt)

Strato-volcano

Steeper slopes, explosive tephra, magma is andesite

This forms mostly from ash deposits

Cindercone

This is composed of multiple layers of ash and rock

Strato-volcano

Which geologic time principle places events in order based on their position?

Relative time

When was the extinction of the dinosaurs?

66 million years ago

What year was the oldest fossil found?

500 million years ago

When was the Earth formed?

4.6 billion years ago

What are the 2 types of surface waves?

Rayleigh waves and Love waves

Rayleigh waves

Vertical movement of surface

Love waves

Produced horizontal movement

What are the Eons of geologic time?

Archean, Proterozoic, and Phanerozoic

What are the Eras of geologic time?

Paleozoic, Mesozoic, and Cenozoic

How long ago was Archean?

5000 million years ago

How long ago was Proterozoic?

2,500 million years ago

How long ago was Phanerozoic

541 million years ago

How long ago was Paleozoic?

541-252 million years ago

How long ago was Mesozoic?

252-66 million years ago

How long ago was Cenozoic

66-0 million years ago

What are the two mass extinction that occurred in geologic time?

Permian-Triassic and Cretaceous-Tertiary extinction

Permian-Triassic

Elimination of over 95% marine and 70% of terrestrial animals.

Cretaceous-Tertiary

Elimination of approximately 80% of all species of animals. Includes the extinction of dinosaurs. Mostly birds survived.

How long ago are the fossils traced back?

500 million years ago

What is dirt made up of?

45% mineral fragments, 25% water, 25% air, and 5% organic materials

Why is soil important?

Allows us to grow crops, water filtration, help with flooding and more

What is weathering?

Physical, chemical, and biological breakdown of rocks and minerals

Physical Weathering

Disintegration of rocks and minerals into smaller pieces

Unloading

Erosion strips away overlying material

Wedging (frost)

Process by which water seeps into cracks in a rock, expands on freezing and thus enlarges the cracks. The process repeats

Wedging (Crystal Growth)

Growth of salt crystals in small rock openings

Chemical Weathering

Decomposition of rocks due to the chemical breakdown of minerals

Dissolution

Minerals in a rock are dissolved by water (ex: acid rain)

Hydrolysis

A chemical reaction in which water reacts with a compound to produce other compounds

Oxidation

Oxygen reacts with iron and other metals to form new mineral compounds (ex: rust on your car)

Microscopic Biological Weathering

Primarily caused by decomposition of material that converts solid material to gases with or without water

Macroscopic Biological Weathering

Includes the actions: Plant roots, animal burrows, termites, and other boring organism

Rock composition

Weathering is faster in rocks composed of weaker material or material that is easily converted to weaker material (such as feldspars) and rocks made up of minerals that dissolve in water (salt). Slower in rocks made up of resistant materials (quartz)

Rock Properties

Weathering is faster in rocks that allow air and water (porous, fractured). Fractures are natural weathering surfaces.

Name the layers in Soil

O: Organic debris, dead leaves, and plant, and animal remains, makeup 30% of this layer.
A: Topsoil, dark organics mixed with mineral grains by organic activity
E: Subsurface layers that have lost most of their minerals. Can be embedded in A horizon or replace A horizon
B: Subsoil, accumulation of iron, aluminum, and clay leached down from the A and E horizons
C: Weathered, lowest rock layer, partially broken down the bedrock

Mass wasting

The downslope movement of materials under the influence of gravity (landslides)

What are some factors influencing Slope failures?

- Gravity moves materials down a slope (Gravity has 2 components: parallel to the slope and perpendicular to the slope)
- Friction acts to prevent or movement of material down a slope
- Steeper slopes are more likely to fail

What happens when there are too much water?

- promotes instability
- very wet sediment flows like a liquid
- Excess water reduces cohesion between grains and allows them to move more freely
- Adds weight to the slope
- Water supports some of the weight of overlying materials

How can we minimize slope failures?

- Improve slope drainage
- Attach the slope material to bedrock with physical restraints
- Build a restraining wall
- Urban planning
- Careful of deforestation

What types of slope failures are there?

Rockfall, Rockslide, Slump, and Creep

Rockfall

A descent of loose rocks

Rockslide

Large-scale movement of rocks down a hill

Slump

Movement of material down a slope on a curved surface

Creep

Slow, downslope movement of soil and earth materials

Why are Rivers important?

Good for farming, soil has moisture/sediment, river deposit silt for goods, easy transportation for goods, good for hunting, and hydroelectricity

Stream

Any flow of water through a channel (defined by its banks), from the smallest creek to the biggest river

Hydrologic Cycle

Water moves in and around the earth system, changing from one physical state to another

Where do streams come from?

Comes from uphill and orginates from a springs

What is an aquifer?

A body of rock and sediment that's saturated - water is in it and around it. And water can move through it

Where does water go?

Regardless of where or how it starts, streams always flows downstream and empty into another body of water (stream, lake, ocean, reservoir, wetland)

What controls the amount of water in a stream channel?

The size of the area it drains and the average precipitation over the area

Drainage Basin

The area drained by a stream and its smaller streams (tributaries)

Drainage Divides

Found along the high ground separating drainage basins

Dendritic pattern

Develops on relatively uniform bedrock

Trellis pattern

Develops in areas of alternating weak and resistent rock

Rectangular pattern

Develops on highly jointed bedrock

Radial pattern

Develops on isolated volcanic cones or domes

Gradient

The slope of the stream. it is the change in elevation of the stream over a horizontal distance

Channel Roughness

Rocky banks and channels -> becomes less rock, changing to gravel, the sand, then fine-grained silt and mud

Wetted Perimeter

Height + Length + Height

Cross-sectional Area

Height x Length

Hydrolysis Rate

Height x Length / Height + Length + Height

Drainage Rate

Volume/Time = m^3/seconds = Height x Length x
Volume

Stream Discharge

Volume of water that passes a given point in one second
(Width x Depth x Velocity = ... m^3)

Groundwater

Water held underground in the soil or in pores and crevices in rock

What are some potential threats to the water supply?

Fertilizer, oil spills, pesticides, bacteria, usage, chemical spills, gasoline stored underground, but mostly caused by human activity

How does water get underground?

The amount of groundwater at any location depending on porosity and permeability materials beneath the surface

Porosity

The proportion of a material that is made up of spaces (Sand, gravel)

Permeability

The capacity of water to flow through earth materials (coffee beans)

Specific yield

The groundwater that can drain from a rock or sediment

Specific retention

Water on the surface of grains that will not flow through the material

Aquitards

Low permeability materials such as clay, shale, or unfractured igneous or metamorphic rock that act as a barrier (ziplock bags)

Unconfined aquifer

Open to Earth's surface and to infiltration

Confined aquifer

Overlain by less permeable materials

Water Table

The level below which the ground is saturated with water

Gaining Streams

Gain water from an area with a high water table (form of discharge not recharge)

Losing Streams

Flow overground in dry areas and lose water into the groundwater supply

Groundwater overdraft

The supply cannot replenish as fast as we extract it for human use which causes a decline in the water table

Pumping Groundwater

Trying to pump groundwater is like sucking up a spilled drink from a table. No matter how big a straw you use, most of the drink stays on the table top