Topic 2 Earth History Flashcards
(28 cards)
Earth is … years old
Earth is 4.6 billion years old
Earth’s history is divided into …
Eons, eras, periods, and epochs
What are Eons, eras, periods, and epochs based on?
Based on major geologic events (e.g. mass extinction - where atleast 75% of all species go extinct
What is uniformitarianism?
The same processes that happen now happened in the past
What is relative age?
Compares the age of one object or event to another without specifying dates (___ is older than ___)
What is absolute age?
an age specified in years before the present
What is the superposition principle?
Within layers of undisturbed, the older layers will be on the bottom and youngest are on top
What is the crosscut principle?
When layers are disturbed by a feature cutting through one or more layers, the feature is younger than those being cut through
What is Dendrochronology?
growth in trees where the oldest is near the core and the youngest growth is on the outside
What is radiometric dating?
assigning an age to an object based on the radioactive half-life of unstable elements in those materials
What is a half-life?
the time it takes for half the unstable elements to decay
What is 14C Dating?
dating an object based on the 14c decay in organic materials
What are the 3 principle layers of Earth’s interior?
the core, the mantle the lithosphere
What is the inner core composed of?
solid iron and nickel
What is the outer core composed of?
liquid iron and nickel
How far below the surface does the inner core extend to?
~5000km
How far below the surface does the outer core extend to?
~3000km
How far below the surface does the lower mantle extend to?
~200km
How far below the surface does the upper mantle extend to?
~100km
How are Earth’s magnetic fields made?
The movement of liquid metal in the outer core generates electrical current
What is the lower mantle made of?
heated and slowly deforming solid rock
What is the upper mantle (asthenosphere) made of?
softer and weaker rock than the lower mantle
How deep is the lithosphere?
surface level to ~100km
How does the lithosphere sit on the upper mantle (asthenosphere)?
the lithosphere “floats” on top of upper mantle
