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What is the law of superposition?
in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below
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What are cross cutting relationships?
A rock is younger than any rock through which it cuts
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What is a halflife?
The time required for half of a sample to decy
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How can we determine half lives?
When the quantities of the parent and daughter are equal
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What elements make useful geologic clocks?
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What is the half life of 40K?
1.3 billion years
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What is the half life of 238U?
4.5 billion years
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How is 14C dating different from other forms of radiometric dating?
It has a half life 5,730, so it dates more recent things
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What is the Shroud of Turin?
Cloth bearing image of man, used radioactive testing, from 1260-1390
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How does radioactive 14C Form?
- Produced in the upper atmosphere
- Cosmic Rays shatter gas atoms releasing neutrons
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What is the oldest rock on earth?
Precambrian, metamophic rocks
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What is the oldest terrestrial mineral on Earth?
zircon---4.3 billion years
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When did the Archean Period end?
2,500 million years ago
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What is special about 543 million years ago?
The Paleozoic Era began
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What is the age of the Earth?
4.6 billion years old
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What is the half life of 14C?
5730
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Can we calculate the half life of a radioactive element without waiting for half of it to decay?
Yes, when the parent and daughter quantities are equal
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What kinds of evidence makes us more convinced that geochronologic ages are correct?
Weathering
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What is significant about the Cambrian Period of geologic time?
It is the first evidence of abundant fossils
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What is ground water?
Any water in saturation zone
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What is a water table?
The upper limit of the saturation zone
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What is the shape of the water table?
it replicates the topography of the land
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What is permeability?
the measure of interconnected pore spaces, or ability of water to flow through pores
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What is porosity?
The measure or water that soaks into the ground
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What rocks have high porosity/permeability?
Coarse grained rocks
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What is an aquifer?
Permeable rock strata that transmit groundwater freely
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What is an aquiclude?
solid impermeable body that acts as a barrier to groundwater
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What is a perched aquifer?
Small aquifer with a local water table that sits above the main aquifer
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What are some problems with ground water?
- -Use more then put in
- -Ground sinkage
- -Saltwater Contamination
- -Pollution
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How much fresh water does groundwater account for?
24% or 83.3 billion gallons per day
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What is Karst?
Large areas that have been shaped by the dissolving power of ground water
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What are speleotherms?
Dripstone features found in caverns
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What is a stalagmite?
Speleotherms that form on the form reaching upward
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What is a stalacite?
Speoleotherms that form on the ceiling coming down (think icicles)
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What is a sink hole?
depression produced in a region where soluble rock has been removed by groundwater
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How can you determine how fast groundwater moves?
- Velocity= K* (h2-h1)/L
- K-coefficient of permeability
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What is Darcy's Law?
Showed velocity of groundwater flow is proportional to the slope
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How do you find the hydraulic gradient?
HG=(h1-h2)/d
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What is the cone of depression?
The cone groundwater makes from wells
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What is an artesian well?
A well drilled into an aquifer where the hydraulic head is higher than ground surface
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What is a spring?
Where the water table intersects Earth's surface
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What does the unsaturated zone mean?
A mix of air and water
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What is a glacier?
A permanent mass of moving ice made of compressed snow on land
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What are the different kinds of glacier?
- Alpine (mountain)
- Continental
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How do glaciers move?
Slowly!
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How many glacial period have there been in the past 1 million years?
About 10
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How many glacial periods have been in the last 2 million years?
about 30
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How do fossils and oxygen isotopes help in understanding glaciations?
- Helps to tell times or warmth and glaciation
- Normal to high levels of oxygen isotopes means glaciation
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What are Arretes?
Sharp edged ridges
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What are horns?
Sharp pyramid like peaks projecting above surroundings
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What are Cirques?
Bowl shaped depressions with precipitous walls on 3 sides but are open downvalley
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What are hanging valleys?
Where glaciers recede and valleys of tributary glaciers are left standing
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What is a tarn?
Small lake from where a glacier used to be
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What is a fjord?
flooded glacial valley
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What are striations?
Grooves in the glacier
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What is an erractic glacier?
"Rock out of place"
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What is a kettle lake?
A large block left behind
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What are Moraines?
glacial till deposited at the sides and ends of glaciers
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What are Drumlins?
Whale shaped object composed of glacial till
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What is a lateral moraine?
Parallel ridges of debris along the side of glaciers
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What are medial morraine?
The middle part of the glacier
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What are ground moraines?
At the base of the ice
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What are the 3 cycles of the Milankovitch Cycle?
- 1. Eccentricity
- 2. Change in tilt of Earth's rotational axis
- 3. Change in precession of Earth's rotational axis
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What causes seasons?
Rotational axis tilt causes seasons
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What is plastic flow?
Movement within the ice
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What is basal slip?
Meltwater acts as a hydraulic jack and helps move ice over rock
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What is Firn?
The granular recrystallized snow
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How many kilometers are in a mile?
1.6
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How many Liters in a gallon?
4
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How many pounds in a kilogram?
2.2
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How many inches in a centimeter?
2.54
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