geological time

Question 1

What is uniformitarianism

Answer 1

physical processes that we observe today operated the same way in the geological past. We use modern processes to help understand ancient events

Question 2

What are aging characteristics of horizontal areas

Answer 2

• strata usually form long horizontal sheets
• subsequent erosion dissects once continuous layers
• flat laying layers are unlikely to have been disturbed

Question 3

What is superposition

Answer 3

layers of rock in which the oldest is the bottom and layers continue to form on top

Question 4

What are characteristics of cross cutting relations

Answer 4

• younger features cut across older features
• faults, dikes, erosion, etc., must be younger than the material that is faulted, intruded, or eroded.
• a volcano cannot intrude rocks that aren’t there yet

Question 5

What are inclusions

Answer 5

a rock fragment within another

Question 6

What rock is older the inclusion or enclosing material

Answer 6

inclusion

Question 7

what is a baked contact

Answer 7

rocks that surround a pluton that are thermally metamorphised by contact heating

Question 8

What is the main characteristic of baked contacts

Answer 8

the baked rock must have been there first (be older)

Question 9

what is a fossil range

Answer 9

the first and last appearance of a fossil in the rock record

Question 10

what are characteristics of fossil ranges

Answer 10

• each fossil has a unique range
• overlapping ranges provide distinctive time markers

Question 11

what does using fossil ranges allow us to do

Answer 11

correlate strata locally, regionally, and globally

Question 12

what is an unconformity

Answer 12

a time gap in the rock record due to non deposition or erosion

Question 13

what are the three types of unconformity

Answer 13

angular, nonconformity, and disconformity

Question 14

what is angular unconformity

Answer 14

erosional surface between tilted rocks and overlying flat layers

Question 15

what are nonconformities

Answer 15

metamorphic or igneous rocks overlain by sedimentary strata

Question 16

What are disconformities

Answer 16

erosional gap between parallel layers of sedimentary strata

Question 17

what are stratigraphic columns

Answer 17

diagrams drawn to scale accurately showing thickness

Question 18

what is lithographic correlation

Answer 18

the process of matching rock layers from different geographic location based on physical characteristics

Question 19

what do the oldest rocks date back to

Answer 19

3.96 Ga

Question 20

what is the age of the earth

Answer 20

4.55 Ga based on correlation with meteorites

Question 21

What is the earliest evidence of life we have found

Answer 21

roughly 3.7 billion years old during PreCambrian era

Question 22

Multi cellular life didnt form until…

Answer 22

700 million years ago

Question 23

what process create(d) oxygen

Answer 23

photosynthesis

Question 24

what were the first life forms

Answer 24

single cell microbes called stromatolites

Question 25

What was the process of oxygen creation and release

Answer 25

No O2
O2 absorbed by oceans and seabed rocks
O2 starts to gas out of the ocean but is absorbed into land surfaces
Oxygen sinks filled and O2 starts accumulating in atmosphere

Question 26

When did a life form with “hard components” first develop?

Answer 26

542 million years ago as critters with hard shells

Question 27

What is the Cambrian explosion

Answer 27

the starting point for life on the planet