Flashcards in Geologic Time Scale & Age of Earth Deck (64)
______ time puts numbers and dates on things
The geologic time scale is a way of ________ the different time periods - and the whole time the earth has been in existence.
The geologic time scale is a visual ________ of geologic time
What is the geologic time scale?
a visual representation of geologic time
The geologic time scale is based on...
the succession of rock layers
The geologic time scale is divided into:
Eons-> Eras -> Periods -> Epochs
What is the Precambrian supereon?
the period of time on the Earth before there was any life on Earth
About 600 million years ago we began which eon?
The Phanerozoic eon includes which three eras?
Paleozoic, Mesozoic, Cenozoic
The Paleozoic era was marked by...
single cell life that developed into mostly ocean-dwelling creatures
The Paleozoic era was marked by ______ cell life that developed into mostly ocean- ______ creatures.
The Mesozoic Era was the Age of the...
The Cenozoic Era has been named the Age of the...
which eon are we currently in?
the Phanerozoic eon
which era are we currently in?
the Cenozoic era
What are Eras further divided up into?
how long to periods last?
millions of years
The starting and ending dates of most periods are based on...
Some period boundaries are marked by ______
Periods are further subdivided into...
Some of the earliest attempts at estimating the Age of the Earth are based on...
sedimentation, and thickness of the strata
The earliest attempts at estimating the Age of the Earth looked at a series of rock _____ and figuring out how long it might have taken to ______ all of those rock units.
To conduct accurate estimations of the age of the earth based on sedimentation you would need to assume that there was...
a constant record of deposition and no weathering/erosion
Sir Halley came up with a method to estimate the age of the earth by looking at...
the oceans, and how much salt is dissolved in the oceans.
Sir Halleys theory is that if you could assume that the oceans were originally ________, how long would it have taken for them to accumulate the amount of _____ that they have today
By using Sir Halley's method what was the estimated age of the earth?
90 million years.
What were the flaws of Sir Halley's method?
- you need to assume that the ocean started at 0% salinity (which isn't necessarily true)
- you need to assume that the salt content doesn't vary (which isn't necessarily true: salt content can be lost through tectonic, biologic processes)
How can salt content be lost in the ocean?
through biologic, tectonic processes
What was Darwin's estimate of the age of the earth based on?
the time it would be necessary toe rod a particular mountain range in Europe