Geology and Earth Science Flashcards
Magma Intrusions
Volcanic Activity
Fault Lines
Earthquake/Tectonic activity
Absolute Time
The actual or estimated date of an event.
[Ex. The Wooly Mammoth first appeared 1.7 million years ago (MYA) ]
Relative Time
Placing historic evens in proper sequence order, relative of other events.
The Geologic Time Scale is organized into periods of relative time.
Fossils
Preserved remains or traces of living things
Index Fossils
A special fossil that allows geologists to determine the relative age of rock layers in which they are found.
(They can match up rock layers at locations that may be far apart).
Fossil Dating
Carbon-14 is used to determine the age of past-living things. It’s can date as far back as 60,000 years.
Carbon-14
Used for fossil dating, the amount of carbon-14 remaining determines how long ago an organism lived. Carbon-14 decays over time.
(The less carbon-14 there is, the longer time ago).
3 Types of Rocks:
- Igneous
- Sedimentary
- Metamorphic
Igneous Rock
Form from the cooling of liquid rock; made from lava. These are classified based on composition and texture.
There are intrusive and extrusive igneous rocks.
Intrusive Rock
A type of igneous rock which cools inside the Earth and often have large crystals inside them.
Extrusive Rock
A type of igneous rock which cools outside the Earth, usually from volcanoes.
Half Life
The time it takes for half of a radioactive element’s atoms to decay (Carbon-14).
Laws of Relative Dating
Used to identify the relative age of rock layers.
- Law of Superposition
- Law of Cross-Cutting
- Law of Faulting
Law of Superposition
In undisturbed sedimentary rock, the youngest rock layers are on top and the oldest rock layers are on the bottom.
Law of Cross-Cutting
Intrusive Igneous rock is younger than the rock it cuts through.
- Cools slower, inside the Earth.
Extrusive Igneous rock is younger than the rock it lies on.
- Cools faster, outside the Earth.
Law of Faulting
A fault is a crack in the Earth’s crust along which movement has occurred.
Faults are younger than the rock they have broken.
Unaffected rocks will be older than the rocks made due to faults.
Unconformity
A gap in the rock record (Some rock layers are missing) usually caused by weathering and erosion.