Review sheet #2
7,4,14, 17, global warming
Metamorphic Rocks - Chapter 7
Metamorphic Rocks - formed by high amounts of heat and pressure. Usually caused by tectonic activity
Regional Metamorphism (large scale)
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Cause: mountain building
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 convergent boundaries (continental-continental) examples: Appalachians, Himalayas
Contact Metamorphism (medium scale)
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Cause: magmatic intrusion (plutonic) metamorphoses surrounding country rock, may form a roof pendant
 convergent boundaries (subduction zones)
Cataclastic (Fault Zone) Metamorphism (small scale)
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Cause: changes caused by heat and pressure of moving fault blocks
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 convergent boundaries (mountain-building), transform boundaries example: Coastal Ranges of California and rocks along the San Andreas Fault.
Changes due to Metamorphism
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Recrystallization of existing minerals, especially into larger crystals;
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Mineralogical Change as of new minerals develop some of the old ones disappear; and
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Foliation – Reorientation of existing mineral crystals and growth of new ones in parallel or nearly parallel planes.
Foliation (from least to most intense)
 slaty cleavage: mica crystals, not visible to the naked eye, become aligned so they are parallel (applies to slates and phyllites)
 schistosity: mica or hornblende crystals grow big enough to give the rock a platy or “glittery appearance”
 gneissic banding: Mineral migration occurs and dark and light silicate minerals separate, giving the rock a banded appearance rocks to identify: schist, gneiss, quartzite, marble, slate
Chapter 4 - Igneous Activity volcano - mountain composed of successive layers of lava flows and/or pyroclastic materials
Nature of volcanic eruptions (lava flows vs. pyroclastics) - dependent on viscosity of magma, which is dependent on:
1. temperature (increase in temp. decreases viscosity)
2. presence of dissolved gas, usually decreases viscosity, although expansion of water vapor causes a more pyroclastic eruption)
3. (most important) - increasing silica content of magma increases viscosity
Volcanic structures
1. Shield volcano - composed primarily of fluid basaltic lava flows
-large in area, elevation, very gentle slope. Ex: Hawaii
2. cinder cones - composed primarily of volcanic ash and /or other pyroclastic material, usually granitic in composition, example Sunset Crater, Arizona
-small in area, very steep slopes
-often occurs at the end of a volcanic episode, when the last of the magma is getting cool and viscous
3. Composite cones or stratovolcanoes - composed of alternating layers of lava flows and pyroclastics, usually andesitic in composition. Example: Ring of Fire volcanoes (Mt. St.
Helens)

4. Fissure eruptions - volcanic activity that does not come from a central vent. Example:
Columbia Plateau Basalt Flows
Volcanic structures discussed in your reading include volcanic neck, volcanic vent, caldera, nuee ardent, lahar
Hawaiian examples of volcanism
1. fluid, mafic magma, coming from the deep interior of the earth (intraplate volcanism) aa - thicker, jagged pahoehoe - smooth, ropy or braidlike
2. shield volcanoes
3. tends to form fountain-like eruptions, little or no explosive character
Andes/Cascades example
1. viscous andesitic (intermediate) type magma caused by nearby subduction zone
2. tends to erupt explosively, with significant amounts of gas and pyroclastics
Intrusive Igneous Activity mostly connected with volcanic activity, fig 4.20, p. 83
Pluton – structure that results from emplacement of igneous materials at depth. Fig 4.20, p. 83
Exposed by uplift and subsequent erosion of overlying rocks.
Classified by orientation to host rock, either concordant (parallel, sill) or discordant (cuts across, dike)
Batholith - a large intrusive igneous body with an exposure of more than 40 sq. miles
Usually felsic in composition
Partial Melting - production of a magma with a higher silica content than the parent rock
How the crust/upper mantle melts to produce magma
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Raising the temp
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Lowering the confining
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Water and other Volatiles are introduced, since they lower melting point e.g. at subduction zones where wet ocean slabs plunge into mantle fig 4.25, p. 87.
Partial Melting and Magma composition –
Igneous rocks melt over a range of over 200 deg C
Silica-rich (felsic) magma starts to melt at about 750deg C in a near-surface environment
Basaltic (mafic) magma starts to melt at about 1000 deg C in a near-surface environment
Rocks with the lowest melting points will melt first
Most often melting process is not complete; more ferromagnesian minerals stay solid, do not make up remaining magma composition.
Important consequence of this is partial melting : production of a magma with a higher silica content than the parent rock. This is .
Distribution of magmas fig 4.26, p. 88.
Felsic/Andesitic – continental volcanoes
Basaltic – oceanic, but occurs on the continent as well
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Igneous activity at Spreading Centers: Iceland, Mt. Kilamanjaro
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Igneous activity at subduction zones: Ring of Fire volcanos
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Intraplate Igneous Activity (hot spots): Hawaii, Yellowstone
Chapter 14 - Earthquakes

Mechanism of earthquake
 why they tend to occur at plate boundaries
 focus, epicenter
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 elastic deformation, elastic rebound foreshock, aftershock
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Earthquake Magnitude:
 measures energy released
 the same value for a particular earthquake, regardless of where measure

 logarithmic –
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Richter Scale
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Moment Magnitude Scale
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Seismology - study of earthquake waves
 p-waves, compressional - particle motion parallel to direction of wave travel
 s-waves, shear - particle motion perpendicular to direction of wave travel
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Epicenter location using p-waves and s-waves
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Properties of Seismic (Earth) waves
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Change in velocity with change of medium
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Reflection and refraction (bending) with change in medium
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Loss of s-waves with change to a fluid medium
Chapter 17 – Mountain Building
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Rock deformation
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Brittle deformation (fractures, faulting)
Elastic deformation
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Ductile (plastic) deformation (folding)
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Folds - mostly caused by compressional stress
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Anticlines – oldest strata found in center after erosion
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Synclines – youngest strata found in center after erosion
 plunging folds – compressed at an angle relative to horizontal plane.
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Faults-fractures in the crust along which movement has occurred.
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Dip-slip- Primarily vertical movement.
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Normal fault (Tensional) - hanging wall drops down relative to foot wall
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Horst and graben (tensional) Double normal faults with 2 down-dropped blocks and a higher block between them
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Reverse fault (Compressional) - foot wall drops relative to hanging wall
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Thrust fault (Compressional) - low angle reverse fault
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Strike-slip- Primarily horizontal movement. San Andreas Fault System (Box 17.1)
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Mountain Types
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Volcanic (studied in Chapter 4)
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Fault-Block mountains- associated with tensional stress on the crust.
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Folded (complex) mountains - major mountain chains, such as Alps, Himalayas, Urals, etc., caused by folding from convergence.
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Types of Orogenies
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Andean-type convergence (continental-oceanic or oceanic-oceanic subduction)
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Volcanic Mountains (which may erode to expose intrusive core)
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Accretionary Wedge
 California’s Sierras and Coastal Ranges as examples
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Himalayan-type convergence (continental collision)
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Urals, Appalachians, Alps and Himalayas
Global Warming - www.ngdc.noaa.gov/paleo/globalwarming/home.html
Global Warming – observation that the atmosphere near the Earth’s surface is warming, without implications for cause or magnitude.
Greenhouse Effect – term which refers to the way in which some gases in the atmosphere trap heat in the same way as a greenhouse,
Greenhouse Gases: CO2, water vapor, methane, and to a lesser extent, chlorofluorocarbons
(CFC’s) and ozone.

Greenhouse Warming – Global warming due to increase in Greenhouse gases in the atmosphere
Methods of studying Global Warming

Satellites – over the last 20 years
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Instrumental temperature measurements (using thermometers, rain gauges, barometers etc) since about 1860, shows mean annual surface air temps have risen about .5 deg C
(almost 1 degree F).
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Paleoclimatic data – can indicate climatic changes in the context of the last several centuries to the past millennia
Paleoclimatology - the study of past climates, those that existed before humans collected instrumental weather data.
Proxy Climate data – environmental data taken from natural recorders of climate variability. If you can reliably date the material in question, you can use it to match climate changes with time periods in the recent and not-so-recent past.
Oxygen Isotope Analysis - based on the ratio between O16(common) and O18 (heavy).
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Glacial ice composed of snow that originated as water vapor from world ocean.
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Warmer global temperatures cause more O18 to evaporate than colder temps
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Warmer global temps mean ocean is relatively depleted of O18 (since more of it evaporated
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Ice cores – increase in O18 indicates warmer temps
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Coral reefs - O
2
source is the ocean - decrease in O18 indicates warmer temps
Other proxy climate data
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Amount of CO2 in gas bubbles trapped in ice cores
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Sediments, Fossil pollen, in lakes or in the ocean
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Tree rings
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Historical documents
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Rocks and their fossils
Thermohaline Circulation – currents caused by variations in density (from salt content) and temperature
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The end of the North American Drift (continuation of the Gulf Stream)
Man’s Role:
 increase in CO
2
in the atmosphere (Data from Mauna Loa observatory)
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Loss of rain forests to development, agriculture
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Rate of temperature increase different than other periods of climate change