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55 Cards in this Set

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  • Back
Relative Age
Clues to the actual time that the events took place may be present.
the part of a rock formation that is exposed on the surface of the ground
a theory, now discredited, that the geologic features of Earth were formed by a series of sudden violent catastrophes rather than a gradual evolutionary process. A more recent version of this theory holds that the evolutionary process of geologic development has on occasions been supplemented by such catastrophes.
Absolute Age
The amount of time that has elapsed since the rock formed.
moved from their original location, are now known to have been deposited by glaciers during the last Ice Age were used by Catastrophists as evidence of sudden catastrophic flooding.
ordering of layers; the fossils the rock layers contain and consquently at the heart of relative age dating.
Sedimentary rock layers
Believed a great globe-engulfing sea laid down all of the earth's rocky layers, gradually exposing them as the water slowly receded.
Neptunists lost their case to Plutonists, who insisted that crystalline rocks such as granite were not chemical precipitates but had crystallized from a molten state.
"Theory of the Earth" by Hutton proposed that the earth is powered by its own internal heat, is in continuous but gradual change, and is constantly decaying, renewing, and repairing itself.
River Jed-vertical layers of rock worn down by erosion were covered by horizontal beds
Cross-cutting relationship
younger sequences truncates an older one.
Faunal Succession
Individual rock layers can be "fingerprinted" and correlated(or traced) from one place to another on the basis of the fossils they contained.
Stratigraphic Column
Arranging each of the rock layers into a vertical sequence. younger upon older strata
The present is the key to the past
Rule of inclusions
The rule that holds that fragments of one rock in a layer of another must be older than the layer itself.
Rule of Cross-cutting relationships
James Hutton-holds true that any feature that cuts across a rock must be younger than the rock it cuts.
Succession of sedimentary strata
Ancient Life
-first fish, first land plants, first amphibians & reptiles, abundent coal-forming swamps
Middle life
-Pangea, first dinosaurs, break up of Pangea, first mammals, Sierra Nevada, birds, Rocky Mountains, extinction of dinosaurs
Recent Life
-Formation of the Alps, Himalayas, San Andreas Fault, earliest Hominids, Ice Age Begins, humans, ice age ends
4 largest intervals of geologic time, some with durations of billions of years
-starts with the Earth's oldest known rocks
earlier life, which contains the first record of multicellular organisms and visible life
visible life, during which fossils became abundant.
Hadeon Eon, Archeon Eon, Proterozoic Eon
Named for the periods after places where rocks of that age are found
Index fossils
Fossils that were useful for the subdivision bc they were easily recognized
Shorter geologic periods
refers to the exactness of an estimate whereas accuracy refers to its correctness
Henri Bequerel discovered that the atoms of some chemical elemets are inherently unstable and break down in a predictable fashion.
whenever the number of neutrons in the atomic nucleus of a chemical element varies.
Mass Number
Isotopes are identified not by their atomic number but by their mass number. The sum of protons and neutrons in their atomic nuclei
If the new isotope produced by this radioactive decay is also radioactive, several breakdown steps from the original radioactive parent isotope may be necessary to form the final stable nonradioactive daughter
Exponential decay
The process whereby the amount of the parent isotope is halved in each successive half life
Hadeon Eon
The interval between the Earth's oldest rocks and the formation of the planet.
Continental Drift
Wegener proposed that the continents of Europe, Africa, and the Americas were once joined.
Pangea or Pangaea
Meaning all lands.
name of the supercontinent
Wegner's reconstruction of the southern continents into a portion of Pangea know refered as Gondwanaland.
The resulting magnetic field is very weak but it can be detected and its origination measured with a highly sensitive instrument
The study and measurement of the Earth's magnetic field from these ancient rocks
Polar wander curve
The line connecting the changing positions of either pole suggested by successively older basalt samples from a given continent
Apparent polar wander curves
The polar wander curves only trace apparent (rather than actual) polar movement
Magnetic Polarity Reversal
Earth's magnetic field periodically reversed itself
Magnetic epoches
Major magnetic reversals
-every million years or so
Magnetic events
shorter flips
-lasting a few thousand years to a few ten thousand years
Normal Magnetic polarity
North ends of all compass needles have pointed towards the north magnetic field
Reversed magnetic polarity
The north end of a compass end would have pointed toward the South Pole
Magnetic anomaly
odd magnetic pattern
ex.-the floor of the Atlanic Ocean by Iceland
Mid-ocean ridges
Mountain chain under the ocean
Sea floor spreading
Harry Hess
-circulating currents under the ocean floor cause molten rock or magma to ooze up beneath mid-ocean ridges as the sea floor spreads away on each side
Pillow lavas
Distinctive bulbous flows of lava characteristic of formed submarine basalt adn great fissures in the seabed
Deep ocean trenches
Narrow curved depressions in the ocean floor that can reach depths of over 11 Kilometers and extend for thousands of kilometers
Benioff zones
The progressive increase in the depth to the foci of these earthquakes was now seen to reflect the violent descent of oceanic crust back into the Earth's heated interior
The point in the earth's interior at which an earthquake is generated