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45 Cards in this Set

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Scientists who study the Earth are called...
Geologists
What is absolute age?
Time, measured in years, since an event occurred.
What is relative age?
Age of one event compared to another.

(No exact numbers -- just determining whether one event is older/younger than the other)
What are the three groups/families of rocks?
1) Sedimentary
2) Igneous
3) Metamorphic
How are igneous rocks formed?
"Ignis" is Latin for 'fire'.
These rocks were once in a hot, liquid state.
1) Lower crust becomes so hot in places it melts rock
2) Molten (solid->liquid) rock called MAGMA while beneath the ground
3) Rock layers above molten rock create pressure, forcing magma up through weaknesses in the crust
4) Molten rock escapes to surface
5) Once on Earth's surface, molten rock is called LAVA
What is lava?
Molten (melted) rock on the Earth's surface.

Note: This molten rock, after it has solidified on the Earth's surface, is also called LAVA.
What is MAGMA?
Magma is molten rock beneath the Earth's surface.
What is the difference between MAGMA and LAVA?
Magma: molten rock beneath the Earth's surface

Lava: molten rock on the Earth's surface
What two forms can lava take on the Earth's surface?
1)LIQUID: Magma flowing out on the Earth's surface.

2)SOLID:Fine particles of lava sprayed out of a volcanic vent (=ASH)
What are VOLCANIC rocks?
Rocks formed of either lava or ash.
What are some examples of volcanic rocks?
1)basalt
2)obsidian
3)pumice
What is PLUTONIC rock?
An igneous rock that has cooled and crystallized beneath the Earth's surface (also called INTRUSIVE rock).
What kind of rock is granite?
A plutonic (igneous) rock formed from the slow cooling of underground magma.
What is sedimentary rock?
Rock formed from layers of sediment pressed together.
Sedimentary rocks usually consist of rock fragments, such as ________(3) that have been squeezed together.
1) mud
2) sand
3) gravel
Define WEATHERING.
The physical or chemical breakdown of exposed rock.
CAUSED BY: water, wind, and/or ice
END PRODUCT: fragments such as mud, sand, or gravel.
What happens to rock on the Earth's surface once it has been broken down (by weathering) into fragments?
The fragments are carried by waterways (ie. rivers) and end up on the sea floor in settled layers (called SEDIMENT). May later form sedimentary rock.
Name some common sedimentary rocks.
1)mudstone (from mud)
2)shale (from clay)
3)sandstone (from sand)
4)conglomerate (from gravel)
5)limestone
What are fossils?
Plant or animal remains preserved in the Earth's crust, often in these forms:
1) shells
2) bones
3) imprints
4) traces
In what type of rock are fossils often found?
Sedimentary rock
What are metamorphic rocks?
Igneous or sedimentary rock that was changed through the action of heat and pressure under ground.
What are metamorphic rocks?
Igneous or sedimentary rock that was changed through the action of heat and pressure under ground.
What are metamorphic rocks?
Igneous or sedimentary rock that was changed through the action of heat and pressure under ground.
What is a good example of metamorphism?
1) The change from MUDSTONE or SHALE (sedimentary rocks) TO the metamorphic rock, SLATE.

2) LIMESTONE recrystallizing to form MARBLE.
What are geological STRUCTURES?
Features produced after rock has been formed.
Name six common geological structures.
1)fractures
2)faults
3)dikes
4)folds
5)erosion surfaces
6)strata
What are FRACTURES?
Cracks in a body of rock.
What are FAULTS?
Fractures (cracks)along which there has been movement.
What are DIKES?
Igneous rocks formed in rock fractures(cracks)when magma is squeezed upwards and later cools.
These geological structures appear as a stripe of different-coloured rock cutting through another rock.
Dikes.
What are FOLDS?
Geological structures that occur when layers of sedimentary rock are squeezed and then buckle.
What are EROSION SURFACES?
Geological structures that occur when rock has been exposed in the past to weathering and erosion and is later reburied.
What are STRATA?
Layers.
In what kind of rock are STRATA usually found?
Sedimentary
How are STRATA formed?
They result from the settling and depositing of different sizes and kinds of sediment in layers, one above another.
What does the LAW of SUPERPOSITION state?
The OLDEST rock layer is at the BOTTOM; the YOUNGEST rock layer is at the TOP.
What does the CROSSCUTTING rule say?
Any event that disturbs a rock is YOUNGER than the rock itself.
What is a PALEONTOLOGIST?
A scientist who studies ancient life forms.
What is an INDEX FOSSIL?
A fossil known to have lived at a particular time in Earth's history.
It indicates the age of the rock in which it was found.
What is the STANDARD GEOLOGICAL COLUMN?
A vertical diagram.
CONTAINS: all the sedimentary layers and fossils ever found on Earth
ORGANIZATION: in order of relative age
What is the STANDARD GEOLOGICAL COLUMN used for?
To find the age of any sedimentary rock layer by comparing index fossils found in said layer to index fossils in the column.
Is radioactivity an example of RELATIVE or ABSOLUTE aging?
Absolute aging.
How does RADIOMETRIC DATING work?
1) A radioactive isotope of an element (called PARENT MATERIAL) is broken down over time into smaller atoms and particles (DECAY PRODUCTS).
2)Decay products increase as parent material decreases.
3)If we know the amount of change and the rate at which the change is occurring, we can calculate the age of the sample.
a. AMOUNT OF CHANGE: the amounts of parent material and decay products
b. RATE OF CHANGE: the decay rate of every radioactive element has been determined experimentally (half-life graph - the amount of time for 1/2 of parent material to decay is constant)
What requirements must be met for an isotope to be suitable for determining absolute age(4)?
1) Some of the isotope must have been present in the original sample.
2) No contamination or loss of the parent isotope or decay products.
3)Isotopes with short half-lives can only be used for dating younger rocks.
4) Isotopes with long half-lives can only be used for dating older rocks.
What is the GEOLOGICAL TIME SCALE?
A kind of Earth history calendar, divided into intervals called eras and periods. Assigns absolute ages to each of the sections of the Standard Geological Column.