Lab exam 2 Flashcards
Stratigraphy
observations of rocks is to study rock layers
Unconformities
are the rock layers incomplete or gaps
Angular Unconformity
tilted sediments or sedimentary rock, period of erosion between the tilting of the older rock a deposition of the younger sediments
Nonconformity
- sediments deposited on top of igneous or metamorphic rock
Disconformity
parallel layers of sediments with a gap in time
Relative Age Dating
form of dating to determine the age of one rock or event relative to another rock or event.
Principe or original horizontality
Sedimentary rocks were as horizontal layers
Principle of Superposition
sedimentary rocks are deposited with the oldest on the bottom and youngest on top
Principle of Continuity-
sedimentary rocks are deposited in wide spread sheet like deposit its
Principle of cross-cutting relations
if a geologic feature cuts another feature then it is younger than the rock/feature it is cutting
Principle of inclusion-
rock clasts are older than the layer that contains them
Absolute age dating
is the actual time that the rock formed often expressed in years before the present.
Radioactive isotopes
decay spontaneously to other isotopes and various forms of energy
parent
Starting isotope is
daughter
Decay products
Half-life
is the amount of time it takes for one half of a given amount of parent atoms to decay to daughter
Steep slope of decay relations
exponential decay
Seismic waves
elastic vibrations that travel through a body waves or along the surface.
Body waves
further classified into S and P waves
S-waves
cause the material to vibrate wave motion, up and down slower
P-waves
side to side, fast side to side
P waves travel
through solid/denser materials faster because the molecules are closer together
Direct wave
- wave that travels through the material parallel to the surface
Incident wave
angle of reflection is equal to the angle of incidence
Critical refracted wave
beds parallel to the layer travels along the boundary
Geophones
generate a small electric current when shaken attached to semiograph
Direct
has the shorter distance
Elastic
refractive
nelastic
direct wave
Map
representation of a portion of the earth’s surface drawn to some scale
Location
title portion of Earth’s surface
Direction-
orientation of the map
6 essential pieces of information
location, direction, scale, date, legend, and source
Scale
how much of the earth’s surface is portrayed on the map
Graphic scale
visually show the distance on the map corresponding to the distance on the ground
Verbal scale
distance ration is expressed in works
Ratio-
distance ration is expressed as a ratio
Date
feature can change
Legend-
explains the symbols
Source
indicates what individual, group, or agency produced the map
Topo
shows the 3-ed geometry of the Earth’s surface in 2-D
Elevation
or the distance above or below sea level
Contour lines
squigles
Hill
cookie cutters
Ridge-
increase earth’s orbit
Depression
bull eyes lowest in venter and hachure marks
Valley
v shape pinging in the uphill direction
Rule of Vs
pointing towards uphill and upstream direction
Geologic map
portraying the distribution of rock units at the earth’s surface
Vertical cross sections
represent the view seen on a vertical slice through the earth
Contacts
lines separating different rock unites
Attitude-
orientation of the strata
Strike
online of the symbol parallel to the contacts between rock units
Dip
- short line pointing in the direction
Horizontal strata
- principle of original horizontality,
Planar dipping strata
- non horizontal attitude of dipping strata indicate the strata has been tilted
Folded strata-
strata have been bent by compressional forces acting within the earth
Limbs-
on either side of the hold
Hinge
center of the fold
Horizontal folds
strata are folded the hinge will remain parallel to the earht’s surface-
Plunging folds
- inclined to some angle
Anticline
A oldest in the center
Syncline-
youngest center
Faulted
caused by compressional, extensional, or shear forces
Compression-
horizontal forces are towards away
Extension
horizontal forces acre directed away
Shear-
slide
Normal
hanging wall moved down
Reverse
hanging wall moved up
Strike slip
horizontal direction