Geologic History Test Flashcards
Principle of Superposition
Oldest layers are at the bottom, youngest at the top.
Olderlayers on the bottom, younger layers on top
Original Horizontality
Sediments are deposited in horizontal layers parallel to the earth’s surface.
Law of Crosscutting Relationships
Anything that cuts across layers (fault, folding, tilting, intrusion, extrusion) must be younger than the layers it cuts across.
Unconformity
a buried erosional surface. Look for “wavy” or irregular lines that have layers on top of them. Formed as a result of erosion and deposition
Contact Metamorphism
Indicated by small black lines. Tells you if the igneous rock is an intrusion or an extrusion based on which surrounding rocks have contact metamorphism.
The letter for each fossil can be found in the _____________________________.
This tells you which geologic ______/______ the organism lived in
Time Distribution of Fossils column on page 9.
period/era
There are different ___________ of fossils (ex: trilobites) that can have more than one index fossil in them. Follow the ______ _________ _________ on page 9. When the gray line ends, that means the organism went _______
categories
vertical gray lines
extinct
Index fossil characteristics
Found over a widespread area and lived for a relatively short period of time (found in only one layer)
You may sometimes have to go to page _ of the ESRT to determine areas of NY that fossils can be found in.
3
Absolute dating is finding
the numerical age of something. Ex: 100 million years
Relative dating is
comparing the ages of two or more layers. Ex: Layer A is older than Layer B.
Some Elements are Radioactive. This means that they emit ________ through the process of __________.
particles
radiation
Radioactive elements are sometimes called
isotopes
Radioactive elements decay (lose particles) at ________ rates.
predictable
They decay into their ________/__________ _________.
daughter elements/isotopes.
