Second Geology Test Flashcards
Elastic rebound hypothesis
Displacement happens. Rocks accumulate energy. Rocks build up stress by plates moving past each other. One day the elastic will bounce back and there will be an earthquake
What is the main reason for earth quakes?
Plate boundaries and their moving. Fault boundaries to be exact ex: San Andreas, California
Transform boundary- earthquakes
Side swipe. Creates earth quakes. There is a seismic gap- friction is holding it back ex: San Andreas fault
Tension - divergent boundaries- earthquakes
Rocks don’t have much strain energy. Pulling apart. Low earth quake waves. Normal fault. People friendly boundary.
Subduction zone- earth quakes
Strike and slip- can be low, medium and high magnitude earthquakes. Earthquakes relates to volcanoes
Magnitude
Relies on the data attained from seismic records to estimate the amount of energy released at an earthquake’s source
Contour line
Lines contacting points of equal elevation
Volcanoes
Opening in the crust, spuing out magma which then is called lava.
P waves
Primary waves. Compressional waves, anything linear will snap. Ex: bridges and electric lines. “Push/pull” waves. They push (compress) and pull (stretch) rocks in the direction the wave is traveling. P waves travel through all materials! Solid, liquid and gas. First to be recorded on seismograph.
S wave
Secondary waves. Shake the particles at right angles to their direction of travel. Liquids and gases will not transmit S waves. Second wave to be recorded and is faster then surface waves.
L wave
Called a long wave and is a wave that reaches the surface. Makes the most damage. Is the surface wave. Last waves to be recorded. Slower then the p and S waves. (Body waves) greatest amplitudes. Cause greater ground shaking and hence greater property dance than either p or a waves
How do you measure and earthquake?
Need 3 different angles of the body waves ( p wave and S wave) the data goes into a seismograph and then prints out on a seismogram.
Intensity
A measure of the amount of ground shaking at a particular location, based on observed property damage.
What is the Richter Scale ?
Is calculated by measuring the amplitude of the largest seismic wave, usually surface (S wave) is used for this this measurement on seismograph pg 198
Seismograms
Provide useful information about the nature of seismic waves. They reveal two main types of waves generated by the slippage of a rock mass. Two types are surface waves and body waves
What are surface waves?
They travel in rock layers just below earths surface. Can be divided in two types of surface waves. 1. Causes earths surface and anything resting on it to move. 2 causes earths materials to move side to side.
What are body waves?
Travel through interior of earth. And can be further divided into two types of waves P waves and S waves.
What are the four factors of damage by an earthquake?
- The intensity
- The duration of the vibrations
- The nature of the material on which structures rest
- The nature of building materials and construction practices of the region
Volcanoes
Opening in the crust, spuing out magma, which is then called lava
Oceanic volcanoes
Are non explosive
Pacific Rim
Has the most volcanoes, is a subduction zone, explosive volcanoes.
Divergence boundary volcanoes
Adding new liquid to the sea floor= non explosive volcanoes
Hot spot
Magma stays at constant position. Ex: Hawaii and yellow stone. Can tell there are hot spots by earthquake waves. S waves don’t transmit through liquid.
Composite cone
Explosive volcanoes. Pacific rim. The greater the solid material the more explosive.
Viscosity
The primary factors that affect the behavior of magma and lava are it’s temperature and composition. Also the amount of dissolved gases it contains. The lack Magma mobility. As lava cools viscosity increases
Earthquakes can cause=
Liquefaction, landslides, fire, tsunami
What countries are near the pacific rim?
Coastal regions of chile, Central America, Indonesia, Japan and Alaska. Also Aleutians islands
Three different types of lavas
Basaltic(Mafic), Andesitic (intermediate) and Rhyolitic
Eruption columns
Only found at highly viscous magmas. Fragments lava and gases are in these clouds coming out at super sonic speeds! Can rise as high as 25 miles. Because the lava is silica rich and the magma is sticky aka viscous.
Basaltic (Mafic) lava
very fluid, generally a thin flow. Streamline ribbons. Low in silica. Low gas percentage. Low viscosity. Shield volcanoes, basaltic plateaus and cinder comes. Pahoehoe is an example of basaltic
Rhyolitic (Felsic) lava
Opposite of basaltic. Very high in silica and gas.
Great viscosity and will have pyro clastic flows. Violent explosions!
As silica content is high it becomes hard for gases to escape
Andesitic (intermediate) lava
Is the middle area of both extremes (basaltic and Rhyolitic)
Medium silica and has counts. Composite cones
Basaltic creates two types of lava flows=
First studied in Hawaii.
AA- have surfaces of rough, jagged blocks with dangerously sharp edges.
Pahoehoe- exhibit smooth surfaces and sometimes resemble the twisted braids of ropes. More fluid then aa. Can change into as flows tho. Aa can not become pahoehoe
Pyroclastic flows
Which consist of hot gases infused with incandescent ash and large lava fragments.
What are lahars?
Is a mudflow made of material from a pyroclastic flow. These are only found to happen by explosive volcanoes.
Uniformitarianism
The physical, chemical and biological laws that operate today have also operated in the geologic past. To understand ancient rocks we must understand present rocks
Numerical date
Dates that specify the actual number of years that have passed since an event occurred. Radio metric dating techniques all us to accurately give a numerical date.
Relative dates
When we place rocks in their proper sequence of formation- echo formed first, second, third and so in. This can not tell how long ago something took place.
Principle of superposition
Refers to sedimentary rock layers. In an undefined sequence of sedimentary rocks, each bed is older than the one above it and younger then the layer below it.
Bombs
Particulars produced during volcanic eruptions that remain molten as they travel through the atmosphere and are greater than 64 mm in diameter
What gases are in basaltic lava?
Water vapor 70% Carbon dioxide 15% Nitrogen 5% Sulfur dioxide 5% And lesser amount of chlorine, hydrogen and argon
Mantel plumes
Producing volcanoes at the Hawaiian island, produced high temperature basaltic lavas with very low viscosity
Order of geologic time scale- oldest to most recent to current time
Paleozoic, Mesozoic and Cenozoic
Phanerozoic
Greek translates to visible life. Represents the last 543 million years of geologic time and contains abundant fossils with hard skeletal parts.
Half life of atom
The time required for one-half of the nuclei in a sample to decay. The rate if radioactive disintegration. Parent and daughter usually have equal 1:1 but when 1:3 happens you know 2 half lives have passed
Who is James Hutton to geology?
He is the father of modern geology. Scottish physican and farmer published Theory of the Earth. Uniformitarianism was born
Who is Nicolas Steno?
Danish anatomist, geologist and priest (1638-1686). First to recognize a sequence of historical events in an outcrop of sedimentary rock layers. He created the principle of superposition
Principle of original horizontality
Steno also created this principle. Layers of sediment are generally deposited in a horizontal position.
Principle of cross- cutting relationships
States that geologic features that cute across rocks must form after the rocks they cut through. Ex: a dike if igneous rock cuts through surrounding rock, makes a baked zone ( contact metamorphism) this intrusion occurred after the surrounding rock was placed
Inclusions
Are fragments of one rock unit that have been enclosed within another.
Ex: inclusions of igneous rock contained in the adjacent sedimentary layer indicate the sediments were deposited atop the weathered igneous mass and this are younger pg 276
Xenoliths
Are inclusions in an igneous intrusion that form when pieces of surrounding rock are incorporated into magma.
Conformable
When layers of rock that have been deposited essentially without interruption.
Unconformities
Represents a long period during which deposition ceased, erosion removed previously formed rocks and then deposition resumed.
- when deposition of a rock is interrupted Which happens all the time. All such breaks in their rocks are recorded.
There are three types of unconformities
Angular unconformity
Consists of tilted or folded sedentary rocks that are overlaid by younger more flat laying strata. This shows that during a pause in deposition a period of deformation (folding or tilting) and erosion occurred.
Disconformity
Is a gap in the rock record that represents a period during which erosion rather than deposition occurred. Pg 277
Nonconformity
In which younger sedimentary strata overlie older metamorphic or intrusive igneous strata .
Transform fault boundaries
Ex: San Andreas fault in Cali. Separates two great sections of earths lithosphere- the North American plate and the peacocks plate. Pg 192 consists of many fractures and is no straight. Each segment behaves differently creating a fault creep
Fault creep
Gradual displacement of fractures in a fault and produces little seismic shaking. Other parts of the fault slip and create small to moderate earthquakes. Other fragments store energy and when that energy is released the earthquake will be severe- elastic rebound theory.
What are the tree types of radio active decay?
Alpha particles, beta particle and electron forms with a proton
Radio metric dating
Provides a reliable method if calculating the ages of rocks and minerals that contain particular radioactive isotopes.
Parent
An unstable/radioactive isotope
Daughter products
The isotopes resulting from the decay Of the parent
AlpHa particles
May be emitted from the nucleus a an alpha particle consists of. 2 protons and 2 nitrons. Pg 285
Alpha emmission
Emission of 2 protons and 2 neutrons. An alpha particle. Mass number is reduced by 4 and the atomic is lowered by2
Beta emission
An electron (beta particle) is given off from the nucleus. Mass number rains unchanged and the atomic number increases by. 1
Electron capture
An electron is captured by the nucleus. Electron combines with a proton to form a neutron. Mass number unchanged and the atomic number decreases by 1
