Geologic Time
The largest units of geologic time are ______________. The smallest units of geologic time are ____________.
Largest: Eons
Smallest: Epochs
These are horizontal layers of rock that form over long periods of time and represent different snapshots of Earth’s history.
Rock strata
Identical index fossils are found in a rock layer in the Grand Canyon and in Utah (675 miles away). What can the scientist infer about the ages of the two rock layers?
They are about the same age
The three major types of fossil fuels.
coal, oil, and natural gas
Two major dangers of mining and burning coal.
air pollution and land/water contamination
How many eons are there in Earth’s history. Name them.
In undisturbed rock layers, the newest rocks are found here.
The top layers of rock strata
The first fossils are of what type of organism?
Single celled organisms
Fossil fuels are considered this because they take millions of years to form.
nonrenewable resources
In which era did birds first appear?
Mesozoic era
This event was the rapid appearance (over a period of many millions of years) of many diverse animal and plant species.
Cambrian Explosion
The age of an event or object in relation to other events or objects in the rock strata is called ______________.
Relative Age
The names of the two processes through which fossils are formed...
Fossilization (per-mineralization) and Impressions (molds/casts)
Fossil fuels were mainly formed during this geologic time period.
Carboniferous Period
Name the time in Earth's history: Clue #1: 65 million years ago to today Clue #2: fossils are in the top layer
Cenozoic Era
Name the time in Earth's history: Clue #1: 4.6 billion to 542 million years ago Clue #2: limited to no Oxygen in air
Precambrian Era
A process that can disrupt rock layers by cutting through existing sedimentary rock. This is when magma rises from the mantle and enters existing rock layers.
Magma intrusions
A well-known fossil group of extinct marine creatures that first appeared in the early Cambrian period. This is a popular index fossil.
Trilobites
Coal forms mostly from this type of matter.
decomposing plant matter (peat)
Coal types are different because of this factor.
Differences in carbon content
Name the time in Earth's history: Clue #1: 251 million years ago Clue #2: Age of Reptiles
Mesozoic Era
Finding shellfish and plankton fossils in a rock layer suggest this about the past environment.
It was an ocean or marine environment
If a large extinction event occurred, what would you expect to find in the rock layer from that time period?
Fossils and high levels of carbon
Oil and natural gas form mainly from these organisms.
tiny marine organisms (e.g., zooplankton)
Geologists look for underground collections of oil and natural gas called these.
Reservoirs