Geological Time

Front 1

Scientists who study the Earth are called...

Back 1

Geologists

Front 2

What is absolute age?

Back 2

Time, measured in years, since an event occurred.

Front 3

What is relative age?

Back 3

Age of one event compared to another.

(No exact numbers -- just determining whether one event is older/younger than the other)

Front 4

What are the three groups/families of rocks?

Back 4

1) Sedimentary
2) Igneous
3) Metamorphic

Front 5

How are igneous rocks formed?

Back 5

"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

Front 6

What is lava?

Back 6

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.

Front 7

What is MAGMA?

Back 7

Magma is molten rock beneath the Earth's surface.

Front 8

What is the difference between MAGMA and LAVA?

Back 8

Magma: molten rock beneath the Earth's surface

Lava: molten rock on the Earth's surface

Front 9

What two forms can lava take on the Earth's surface?

Back 9

1)LIQUID: Magma flowing out on the Earth's surface.

2)SOLID:Fine particles of lava sprayed out of a volcanic vent (=ASH)

Front 10

What are VOLCANIC rocks?

Back 10

Rocks formed of either lava or ash.

Front 11

What are some examples of volcanic rocks?

Back 11

1)basalt
2)obsidian
3)pumice

Front 12

What is PLUTONIC rock?

Back 12

An igneous rock that has cooled and crystallized beneath the Earth's surface (also called INTRUSIVE rock).

Front 13

What kind of rock is granite?

Back 13

A plutonic (igneous) rock formed from the slow cooling of underground magma.

Front 14

What is sedimentary rock?

Back 14

Rock formed from layers of sediment pressed together.

Front 15

Sedimentary rocks usually consist of rock fragments, such as ________(3) that have been squeezed together.

Back 15

1) mud
2) sand
3) gravel

Front 16

Define WEATHERING.

Back 16

The physical or chemical breakdown of exposed rock.
CAUSED BY: water, wind, and/or ice
END PRODUCT: fragments such as mud, sand, or gravel.

Front 17

What happens to rock on the Earth's surface once it has been broken down (by weathering) into fragments?

Back 17

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.

Front 18

Name some common sedimentary rocks.

Back 18

1)mudstone (from mud)
2)shale (from clay)
3)sandstone (from sand)
4)conglomerate (from gravel)
5)limestone

Front 19

What are fossils?

Back 19

Plant or animal remains preserved in the Earth's crust, often in these forms:
1) shells
2) bones
3) imprints
4) traces

Front 20

In what type of rock are fossils often found?

Back 20

Sedimentary rock

Front 21

What are metamorphic rocks?

Back 21

Igneous or sedimentary rock that was changed through the action of heat and pressure under ground.

Front 22

What are metamorphic rocks?

Back 22

Igneous or sedimentary rock that was changed through the action of heat and pressure under ground.

Front 23

What are metamorphic rocks?

Back 23

Igneous or sedimentary rock that was changed through the action of heat and pressure under ground.

Front 24

What is a good example of metamorphism?

Back 24

1) The change from MUDSTONE or SHALE (sedimentary rocks) TO the metamorphic rock, SLATE.

2) LIMESTONE recrystallizing to form MARBLE.

Front 25

What are geological STRUCTURES?

Back 25

Features produced after rock has been formed.

Front 26

Name six common geological structures.

Back 26

1)fractures
2)faults
3)dikes
4)folds
5)erosion surfaces
6)strata

Front 27

What are FRACTURES?

Back 27

Cracks in a body of rock.

Front 28

What are FAULTS?

Back 28

Fractures (cracks)along which there has been movement.

Front 29

What are DIKES?

Back 29

Igneous rocks formed in rock fractures(cracks)when magma is squeezed upwards and later cools.

Front 30

These geological structures appear as a stripe of different-coloured rock cutting through another rock.

Back 30

Dikes.

Front 31

What are FOLDS?

Back 31

Geological structures that occur when layers of sedimentary rock are squeezed and then buckle.

Front 32

What are EROSION SURFACES?

Back 32

Geological structures that occur when rock has been exposed in the past to weathering and erosion and is later reburied.

Front 33

What are STRATA?

Back 33

Layers.

Front 34

In what kind of rock are STRATA usually found?

Back 34

Sedimentary

Front 35

How are STRATA formed?

Back 35

They result from the settling and depositing of different sizes and kinds of sediment in layers, one above another.

Front 36

What does the LAW of SUPERPOSITION state?

Back 36

The OLDEST rock layer is at the BOTTOM; the YOUNGEST rock layer is at the TOP.

Front 37

What does the CROSSCUTTING rule say?

Back 37

Any event that disturbs a rock is YOUNGER than the rock itself.

Front 38

What is a PALEONTOLOGIST?

Back 38

A scientist who studies ancient life forms.

Front 39

What is an INDEX FOSSIL?

Back 39

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.

Front 40

What is the STANDARD GEOLOGICAL COLUMN?

Back 40

A vertical diagram.
CONTAINS: all the sedimentary layers and fossils ever found on Earth
ORGANIZATION: in order of relative age

Front 41

What is the STANDARD GEOLOGICAL COLUMN used for?

Back 41

To find the age of any sedimentary rock layer by comparing index fossils found in said layer to index fossils in the column.

Front 42

Is radioactivity an example of RELATIVE or ABSOLUTE aging?

Back 42

Absolute aging.

Front 43

How does RADIOMETRIC DATING work?

Back 43

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)

Front 44

What requirements must be met for an isotope to be suitable for determining absolute age(4)?

Back 44

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.

Front 45

What is the GEOLOGICAL TIME SCALE?

Back 45

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.