What is the geologic time scale?
The geologic time scale is a system scientists use to divide Earth’s 4.6-billion-year history into different time units, such as eons, eras, periods, and epochs.
What principle states that in undisturbed rock layers, the oldest rocks are at the bottom and the youngest are at the top?
The Law of Superposition.
What is a fossil?
preserved remains, impression, or trace of a once-living organism from the past, usually found in rock.
What major event marks the start of the Phanerozoic Eon (541 million years ago–present)?
The Cambrian Explosion, when many new types of animals with hard shells and skeletons appeared.
What weighs more, a pound of feathers or a pound of bricks?
THEY WEIGH THE SAME
During which era did the dinosaurs dominate Earth?
The Mesozoic Era (about 252–66 million years ago)
If a fault cuts across several layers of rock, which is older—the fault or the rock layers?
The rock layers are older; the fault is younger (Principle of Cross-Cutting Relationships).
What kind of fossil forms from the impression of the behavior of an organism is left behind and cemented?
Trace fossil
What event ended the Cretaceous Period and wiped out the dinosaurs?
A mass extinction caused by a large asteroid impact (and volcanic activity), about 66 million years ago.
Why does soda fizz when you open it?
CO2 is dissolved in the liquid under pressure, so when pressure is released the bubbles form
Which era are we living in today, and what makes it unique?
We live in the Cenozoic Era, often called the "Age of Mammals"
A fossil of a trilobite is found below a fossil of a dinosaur. Which fossil is older?
The trilobite is older, since trilobites lived long before dinosaurs.
What kind of fossil is formed when an organism is covered in rock and decays leaving a void (hole, or cavity) in the rock.
Cast fossil
What was the largest mass extinction in Earth’s history, and when did it occur?
The Permian-Triassic extinction (~252 million years ago), which wiped out around 90–95% of marine species and 70% of land species.
How many layers does the earth have?
3/4
How many eras are there in geologic history?
10
What is the absolute (exact) dating technique geologists use called?
Radioactive dating- Measuring uranium to lead
What are 3 ways something can fossilize?
Amber, ice, cementation of sediment
What was the “Great Oxidation Event,” and why was it important?
About 2.4 billion years ago, photosynthetic bacteria (cyanobacteria) produced enough oxygen to permanently change Earth’s atmosphere, allowing aerobic life to evolve.
What type of event occurs that moves rocks from one place to another? (Hint: this is called a fault)
Earthquake
How many eons are there in geologic history?
2
What is an unconformity, and what does it represent?
An unconformity is a gap in the rock record where erosion or lack of deposition occurred, representing missing time.
What kind of fossil is formed when minerals fill in a void (hole or cavity) and harden into rock in the 3D shape of the organism.
Mold fossil
What is the Quaternary Period known for, and when did it begin?
Beginning about 2.6 million years ago, it is known for repeated ice ages, the evolution of modern humans, and major climate changes.
How old is Mr. O'Brien
24