VOLCANISM, FOLDS, AND FAULTS LECTURE NOTES


VOCABULARY: diastrophism, isostacy, volcanism, plutonism, lava, magma, intrusive, extrusive, batholith, stock, laccolith, dike, sill, volcanic neck, lava flow, fissure, volcano, vent, shield cone, cinder cone, composite cone, pyroclastic debris, quiet, explosive, volatiles, crater, caldera, intermediate, fissure, gasses and vapors, volcanic bombs, blocks, cinders, ash, dust, aa, pahoehoe, pillow, mud torrent, earthquake, seismology, seismograph, focus, Mercalli scale, Richter scale, epicenter, fold, fault, law of original horizontality, cross-bedding, law of superposition, law of cross cutting relations, relative dating, unconformity, contact, geologic map, block diagram, cross section, anticline, syncline, dome, basin, recumbent fold, dip, strike, differential erosion, joint, fault, vertical fault, normal fault, reverse fault, hanging wall, foot wall, hanging wall block, footwall block, overthrust fault, horizontal fault, strike-slip fault, transform fault, fault plane, fault trace, fault scarp, horst, graben, thrust fault, fault-block mountain

diastrophism--folding, warping, and faulting (breaking of the crust)
isostacy--balancing of crust

volcanism--all process which give rise to magma, cause it to move, its expulsion from the earth, and which may refer to near or at surface only

plutonism--refers only to magmatic actions

magma moves toward the surface by: cracking and breaking rocks; melting overlying

•magma--molten rock within the earth
•lava--molten rock at or near the earth's surface

•intrusive--magma and resultant igneous bodies within the earth
•extrusive--lava and resultant igneous bodies at or near the earth's surface

types of intrusive bodies--(molten or solid)

types of extrusive bodies
Igneous Bodies

three types of volcanic cones
types of eruptions
products of eruptions
earthquakes--150,000 a year estimate
seismology--the study of earthquakes

shallow focus 0-20 miles most destructive 95% of all quakes
deep focus 20 - 400 miles 5% of total, 435 miles deepest

Mercalli scale--qualitative Roman numerals, I--XII
Richter scale--quantitative 1-10; effect on seismograph 100 km for epicenter

epicenter--point at earth's surface directly above the focus

distribution

geologic map--shows the rocks at the surface of the earth
block diagram--shows both a surface view and the rocks at depth
cross section--shows the rocks within the earth; the top line is the surface; like looking at a slice cut into the earth

contact--the boundary line between two different rocks (rock units)

reaction to pressure--folding (bending) or faulting (breaking)

Law of Original Horizontality--when sediment is deposited, it is USUALLY deposited in a horizontal layer
•exception--cross-bedding

Law of Superposition--when sediments are deposited, the oldest layer will be found underneath the younger, and they remain this way unless they are overturned

Law of Cross Cutting Relations--when one geologic feature cuts across another, the one which is cut across had to exist beforehand so it is older than the feature which cuts through it

relative dating--dates one event in relation to another

unconformity--a gap in the rock record; erosion has occurred and removed materials form the area and then later more material was deposited on this erosion surface

Relative Dating Diagram 1

anticline--upfold of the rock layers--dip is away from center
syncline--downfold of the rock layers--dip is toward the center
dome--a double upfold of the rock layers
basin--a double downfold of the rock layers
recumbent fold--strongly folded (overturned)

dip--angle between a horizontal plane and a rock layer
strike--orientation in which rock layer is intersected by a horizontal plane, at right angles to the dip direction

differential erosion--it is important to note that the resistance of the rock units is the greatest influence on the topography

rockhumid climatearid climate
limestoneNR
sandstoneRR
shaleNN
coalNN
igneousRR
metamorphicRR

N=nonresistant
R=resistant

joint--a break in the rocks along which no movement has taken place
fault--a break in the rocks along which movement HAS taken place

vertical faults--vertical movement
horizontal faults--horizontal movement

vertical
Vertical Faults

horizontal, lateral, strike-slip, transform--movement is horizontal

Transform Faults

fault plane--the plane of breakage along which movement occurs
fault trace--the line at the intersection of the fault plane with the surface or a horizontal plane
fault scarp--a cliff that results from vertical faulting

Block Fault

horst--a block that has been raised by faulting between two others
graben--a block that has been lowered by faulting between two others

overthrust fault [thrust fault]--(overturned)--very low angle reverse fault

Faults Illustrations Exercise

Relative Dating Rank 1
Relative Dating Rank 2
Relative Dating Rank 3

Relative Dating Diagram 2

Relative Dating Practice

True-False Relative Dating
Relative Dating River Block

three kinds of mountains: folded, faulted, volcanic

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