GEO EXAM 1 Flashcards
Big Bang Theory
13.75 billion years - origin of the universe
Why do scientists think the world is expanding?
Red shift - Doppler effect. Everything in the universe is moving away from everything else.
First material to form
Hydrogen and helium
Where did other elements come from?
Heavier element are formed in stars, process of fusion
Origin of our solar system
Rotating nebula
Energy Sources
Impact energy (meterorite), Gravitational energy, Radioactive decay, Sun
Radioactive Emmissions
Alpha particles, Beta particles, Gamma rays
Internal Sources
Earthquakes and volcanoes - radioactive materials
External Sources
Weather - Sun
Mineral
Naturally occuring inorganic solid, can be expressed by chemical formula
Chrystelline
Orderly and repetitive atomic arrangement
Diamond
South Africa is the largest producer, they form at high pressures and temperatures deep within the earth, hardness of 10
Kimberlite Pipes
Deep explosive volcano
Corundum
Ruby - red, Sapphire - blue, hardness of 9
Turquoise
Found in volcanic rocks, softer, hardness of 6
Quartz
Amethyst, many different varieties - usually in color
Basaltic
50% SiO2, flows easily
Granitic
60-70% SiO2. Viscous - does not flow easily.
The Great Molasses Flood of 1919
Boston - 21 people died and 150 injured. Rescue workers got stuck in the viscous mess
Texture
Size of the crystals, Igenous rock textures
Glassy
No distinct grains, rapid cooling
Aphantic
Fine grained, extrusive, quick cooling
Phaneritic
Course grained, intrusive, magma cooled slowy, igneous rock composition - need to know
Coarse
Granite, felsic (light color), diorite, intermediate
Gabbro
Mafic (dark color), Fine
Rhyolite
Felsic (light color)
Andesite
Intermediate
mafic
(dark color), the origin of magma, originates 30 to 120 miles bewlo the earth;s surface, geometry of intrusive igneous rock bodies
Batholith
Huge mass of coarsely crystalline igneous rocks
Stock
Small Batholith
Dike
Discordant (cuts across layers) igneous intrusion, narrow tubular body of igneous rock
Sill
Tabular intrusive body of igneous rock that is parallel to surrounding layers
Cornices
Overhanging snow on the crater rim
Tree casts
empty space that used to have a tree
Lava tube
Conduits through which lava travels beneath the surface of a lava flow
Columnar joining
Results when magma cools from the outside causing shrinkage, forming a hexagonal joint structure. (Devil’s Tower)
Tephra
Bombs and ash, anything that is thrown into the air during an eruption
Mount St Helens is:
Most active volcano in cascade range
Composite volcano
Alternating layers of lava flows and ash. Tend to erupt explosively.
MSH Eruptive History
formed about 40,000 years ago, nine main pulses of pre-1980
MSH progression
March 20th - earthquake recorded, three days another occurred, March 25th, fractures developed on the glacier surfaces and a number of avalanches and rockfacks occurred. North flank bulge. Largest landslide in history.
MSH Ash flow
Ash and steam begin to rise vertically. The ash column reached an altitude of more than 12 miles.
Lahar
Volcanic mud flow
MSH Aftermath
57 people died, only 3 of the 57 were in restricted zones
Harry Truman
Mt. St. Helens Lodge owner on spirit lake, didn’t leave the mountain
Lava dome
lava which is forced from the vent much like toothpaste from a tube, forming a half-ball shape over the vent.
Sediment
Material that has been transported by a current, 75% of continents are covered by sedimentary rocks
Sedimentary Process
- Weathering - break up of rocks
- Transportation by a current - water, wind, glaciers.
- Deposition
- Cementation
Detridal
Made up of broken particles of pre-existing rocks and minerals. Megascopic pieces.
Chemical
Precipitated from solution. Dissolved elements form together to make a sedimentary rock. Atoms bond and travel.
Sediment Sizes
Gravel, Sand, Silt, Clay
Conglomerate
Composed of gravel. Rounded clasts. Very high energy environment.
Sandstone
Composed of sand sized sediment (2mm to 0.62) Beaches.
Siltstone
Composed of silt sized (0.062 to 0.0004 mm) sediment. Low energy.
Shale
Composed of clay sized sediment. Very low energy environment. Has organic matter and oil in shales.
Limestone
505 calcites. Formed in marine environments. Composed of dead marine organisms. Aquatic animals and plants precipitate calcite.
Halite
Salt
Rock Beds
Layers of sedimentary rock, stratified. Most common feature.
Ripple Marks
Small linear ridges of sediment. Forms when a current moves over sediment.
Cross Beds
Inclined layers within beds. (Zion) Cross beds form as ripples or dunes migrate.
Sedimentary rocks have porosity
Empty space that can be occupied by a fluid. Fluids that make money are water and oil.
Metamorphic Rocks
Rocks that have formed in the solid state in response to changes in temperature and pressure. Parent rock recrystallizes (changes the shape and orientation of crystals), classification of rocks are based on presence or absence of foliation.
Foliation
Planar feature, caused by parallel alignment of platy minerals or banding.
Slate
Fine grained, excellent foliation, slaty cleavage. Breaks along parallel lines. Low grade metamorphism. PARENT ROCK IS SHALE.
Schist
Coarse grained foliated metaphoric rock. Higher temp and pressure. PARENT ROCK IS SLATE.
Gneiss
Course grained banded metamorphic rock. High grade metaphorphism. PARENR ROCK IS A SCHIST.
Non-foliated
Quartzite, Marble
Quartzile
Metamorphosed sandstone
Marble
Metamorphosed limestone
Rock Cycle
All rocks can change into other types. One rock type has never been the same type.
Relative Age Principles:
- Uniformitarianism: The present is the key to the past
- Principle of original horizontality
- Stratigraphic superposition: Younger rocks overlap older rock layers.
- Cross-cutting relationships. Anything that cuts something is younger.
- Faunal Succession: The observed changes in life forms occur in a definite and recognizable order through time. Species change through time and only exist for a short time.
Stratigraphy
The study of stratified rocks. Relies on all of the principles stated. Put the worl’ds rocks in a relative time scale.
Uncomformity
Gaps in rocks, the stratigraphic record are called unconformities.
Goal of stratigrapher
CORRELATION
Unconformity
- Deposition
- Uplift and erosion
- Deposition
- Uplift
- Unconformity
The Great Unconformity
The gap in the rock record between cambrian times
Relative Time Scale
The process of correlation has allowed us to place all of the world’s rocks into a relative time scale.
Cenozoic
Age of mammals
Mesozoic
Age of giant reptiles. And birds.
Paleozoic
Explosion of life. Huge amounts of diversity. Intvertebrates, fish, reptiles, insects, vascular plants
Precambrian
Low diversity of life. First single celled organisms. Simple plants, worms, jellyfish.
How was the relative time scale developed?
Fossils, faunal succession
Kaibab
Sandy limestone - permian age - bathtub ring
Coconino
White sandstone cliffs - old sand dunes. Seperated by a layer of trees.
Red Wall
Mississippian Age - Abundant marine fossils
Absolute Time
Putting numbers on rocks, estimates of the earth’s age
Ideas of earth’s age
salinity of oceans, heat loss, thickness of sedimentary rocks, radioactive decay
Half-life
The amount it takes for 1/2 of the orginial parent atoms to decay to the daughter.
Geologic Time Scale
Orginally based on fossils - now based on radioactive decay
Precambrian (time)
4.6 billion years to 570 million years. Comprises of 80% of earth’s time.
Paleozoic (Time)
540 million years to 250 million years. (explosion of life)
Mesozoic (time)
250 million years to 65 million years. (dinosaurs)
Cenozoic (time)
Age of mammals. 65 million years to the present.
Declination
the angle bewteen magnetic north and true north
