U5 Geologic History and Evolution Flashcards
Geologic history is broken into eras, periods, and epochs based upon
fossil evidence found in bedrock
Which important geologic event in NY occurred just after the Grenville Mountains were starting to erode? (ESRT)
the Iapetus Ocean started to open
(ESRT) Scientists infer that oxygen first began to enter Earth’s atmosphere after the appearance of
oceanic cyanobacteria
(ESRT) Scientists believe the impact of an steroid 65.5 million years ago led to the extinction of
dinosaurs, ammonoids, and many land plants
original horizontality
sediments are deposited horizontally and will remain that way if undisturbed
cross-cutting
magma intrusions will cut across pre-existing rock so the intrusion will be younger than the rock it cuts across
relative dating
finding the age of something by comparing it to something else (Ex: the top layer of the bedrock is younger than the layer below it)
superposition
rock layers form on top of pre-existing rock layers so if left undisturbed the top layer will be younger than the layers below it
superposition
rock layers form on top of pre-existing rock layers so if left undisturbed the top layer will be younger than the layers below it
radioactive dating
using the half lives of isotopes to find the age of something (you will get an actual number such as 40,000 years
radio active decay
the breaking down of an isotope into its more stable form; will be used in absolute dating
half-life
the amount of time it takes an unstable isotope to change half its mass into a stable isotope
index fossils
fossils used to perform relative dating. To be a good index fossil both must be true:
1. the organism in the fossil only existed for a short period of time
2. the organism existed over a wide area
If Earth’s history was represented by a 24-hour clock, how long ago did humans appear?
less than a minute
There are fossils of shells in the limestone upstate. This indicates what?
NY was once a marine environment.
