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Rock Cycle
igneous rock
rock that forms when magma cools and solidifies
Extrusive
fine-grained igneous rock that forms when magma cools quickly at or near Earth's surface
Instrusive
igneous rock that has large crystals and formed when melted inside the Earth's surface. Rock cools slowly and hardens
Microscopic grains
Grains not visible to the eye, extrusive
Fine grains
Sand sized 0.5mm, extrusive or intrusive
Coarse grains
Larger than sand >2mm, intrusive
Felsic, Microscopic Grain
Pumice
Felsic, Fine Grain
Rhyolite
Felsic, Coarse Grain
Granite
Andesitic, Microscopic Grain
Obsidian
Andesitic, Fine Grain
Andesite
Andesitic, Coarse Grain
Diorite
Mafic, Microscopic Grain
Scoria
Mafic, Fine Grain
Basalt
Mafic, Coarse grain
Gabbro
mafic magma
Dark color, low viscosity, Shield cone volcano
andesitic magma
Medium or mixed color, mix of low & high viscosity, Composite volcano
felsic magma
Light colored, high viscosity, Cinder cone volcano
phaneritic texture
igneous rock texture in which minerals are easily visible without magnification
aphanitic texture
A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished.
porphyritic texture
An igneous rock texture in which large crystals are scattered on a background of much smaller crystals.
glassy texture
A texture formed when a rock cools so fast it doesn't have time to crystallize
pyroclastic texture
produced from debris of explosive eruption, has many air bubble canals
pegmatitic texture
a texture of igneous rocks in which the interlocking crystals are all larger than one centimeter in diameter
Laccolith
Relatively small, mushroom-shaped pluton that forms when magma intrudes into parallel rock layers close to Earth's surface.
Batholith
A mass of rock formed when a large body of magma cools inside the crust
Magma structures
volcanic neck
solid igneous core of a volcano left behind after the softer cone has been eroded
xenolith
a piece of rock within an igneous rock that is not derived from the original magma but has been introduced from elsewhere, especially the surrounding country rock.
Dike
Vertical igneous structure
Sill
Horizontal-ish igneous structure
intrusion
Igneous rock formed from magma flowing into existing rock
Aa
Blocky slow moving lava
Pahoehoe
A hot, fast-moving type of lava that hardens to form smooth, ropelike coils
shield volcano
Flatter, mafic lava, composed of mainly Iron & Magnesium. Ex. Hawaii
cinder cone volcano
Short & steep, felsic lava, composed of mainly potassium, calcium, and sodium, pyroclastic flow with tephra
Tephra
bits of rock or solidified lava dropped from the air during an explosive volcanic eruption; ranges in size from volcanic ash to volcanic bombs and blocks
composite volcano (stratovolcano)
Tall & steep, andesitic lava, erupts alternately lava and tephra.
Richter scale
Ranks earthquakes based on ground movement, each increase in whole number is 10x the ground movement (logarithmic)
Richter scale effects
0-2 Not felt
2-3 Little felt
3-4 Ceiling lights swing
4-5 Walls Crack
5-6 Furniture moves
6-7* Some buildings collapse
7-8 Many buildings destroyed
8< Total destruction
movement magnitude scale
A scale that rates earthquakes by estimating the total energy released by an earthquake
Modified Mercalli Scale
a 12 point scale developed to evaluate earthquake intensity based on the amount of damage to various structures
Earthquake
Shaking of the earths crust from the release of energy
elastic rebound theory
The theory that continuing stress along a fault results in a buildup of elastic energy in the rocks, which is abruptly released when an earthquake occurs.
Fault
Surface that a rock breaks and moves along
focus
point inside the earth where the energy for an EQ is released
Epicenter
the point directly above the focus on the earth's surface
seismic waves
vibrations that travel through Earth carrying the energy released from the focus during an earthquake
P waves (Primary waves)
travel through liquids, gases, and solids, pushes and pulls, faster, fastest waves
S waves (secondary waves)
travel through solids only; cause rock to move in a side-to-side or up & down motion, slower waves
L waves (surface waves)
travels slowest, most wide reaching, very destructive cause it travels on the surface and can move up/down, rolling motion
Subduction
The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.
ocean trench
Deep valley in the ocean floor that forms along a subduction zone
island arc
A string of volcanoes that form as the result of subduction of one oceanic plate beneath a second oceanic plate.
James Huttton
1790, first one to theorize a "dynamic" earth
Alfred Wegener
1920, proposed theory of continental drift. Theorized a supercontinent, Pangea, in the distant past
Henry Hess
discovered seafloor spreading through the abnormal young igneous rocks on the ocean floor and offered it as an explanation for mid-ocean ridges
Allan Cox and Brent Dalrymple
Discovered the flipping of Earth's magnetic poles through the cooling of rocks
Fredrick Vine and Drummond Matthews
Used the magnetic patterns on the sea floor as proof for seafloor spreading
divergent boundary
The boundary between two tectonic plates that are moving away from each other, O-O or C-C, forms mafic rocks, shallow EQs, makes normal faults
transform boundary
A plate boundary where two plates move past each other in opposite directions, O-O O-C C-C, Offset features, strike slip faults, shallow EQs
strike-slip fault
occurs at transform boundaries
normal fault
occurs at divergent boundaries
reverse fault
occurs at convergent boundaries
Hot Spots
places where molten material from the mantle reaches the lithosphere, middle of a plate
Convergent Oceanic-Continental
Forms a trench, can cause shallow medium deep earthquakes, volcanoes, and mountains.
convergent oceanic-oceanic
Features: Trenches, volcanoes, shallow medium deep earthquakes, volcanic island arcs
Convergent Continental-Continental
Forms folded mountains shallow medium deep earthquakes.
Weathering
The breaking down of rocks and other materials on the Earth's surface.
mechanical weathering
the breakdown of rock into smaller pieces by physical means
chemical weathering
The process that breaks down rock through chemical changes
Four most prominent forces of erosion
Wind, Water, Glaciers, & Gravity
mass wasting
the downslope movement of rock, regolith, and soil under the direct influence of gravity
Landslide
a slide of a large mass of dirt and rock down a mountain or cliff
Mudflow
the flow of a mass of mud or rock and soil mixed with a large amount of water
Slump
A type of mass movement that occurs when a mass of material moves down a curved slope
Creep
the slow downhill movement of weathered rock material
Delta
a low triangular area where a river divides before entering a larger body of water
Alluvial Fan
a fan-shaped mass of material deposited by a stream when the slope of the land decreases sharply
dissolved load
Dissolved material in water
suspended load
The load contains small rocks and soil in suspension, which can make the river look muddy.
bed load
sand, pebbles, and boulders that are moved along the bed of a stream and that are too heavy to be carried in suspension
Fossil
The preserved remains or traces of an organism that lived in the past
Mold fossil
a space in a rock that has the shape of the remains of a living thing that once occupied that space.
Cast fossil
a model in the shape of a living thing or its remains, it forms when minerals or rock particles fill the space
trace fossil
the preserved evidence of the activity of an organism
Preserved remains
remains of organisms in tar, amber, or ice
mineral replacement
Fossils that preserve the structure of the original organically produced matter without actually preserving any of the original matter
carbon film
a type of fossil consisting of an extremely thin coating of carbon on rock
Index fossil
a fossil known to have lived in a short particular geologic age that can be used to date the rock layer in which it is found
Stratigraphy
the branch of geology concerned with the order and relative position of strata and their relationship to the geological time scale.
Law of Superposition
The top rock layer and its fossils is the youngest and the bottom is the oldest.
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