Geological Time in Strata

Question 1

Define stratigraphy

Answer 1

The study of the layers of sedimentary rock at a macroscopic scale

Question 2

Define the Principle of Original Horizontality

Answer 2

Strata tend to be deposited more or less horizontally

Question 3

Define the Principle of Superposition

Answer 3

In a vertical succession of sedimentary or volcanic rocks, a higher rock unit is younger than a lower one. “Up” is younger.

Question 4

Define the Principle of Lateral Continuity

Answer 4

Upon initial deposition, strata tend extend in all directions until they pinch out or until they grade laterally into a different kind of sediment.

Question 5

Define the Principle of Cross-cutting

Answer 5

A structure that cross-cuts another structure is the younger of the two.

Question 6

Define the Principle of Inclusion

Answer 6

A structure included in another is the older of the two.

Question 7

Principle of faunal succession

Answer 7

Fossils in stratigraphic successions change upward (i.e., with time) in a predictable way. For example, strata containing trilobites always underlie strata containing Tyrannosaurus fossils, which in turn always underlie strata with woolly mammoth fossils.

Question 8

Define index fossils

Answer 8

fossils used to define geological periods

Question 9

Define uniformitarianism

Answer 9

The physical laws of Nature have remained the same since the dawn of time. The Earth may change, but the laws that govern this change do not.

Question 10

Define lithostratigraphy

Answer 10

Process by which strata are correlated given their physical attributes

Question 11

What is lithology

Answer 11

Classification of rock types

Question 12

Lithostratigraphic unit:

Answer 12

A rock unit that can be correlated (mapped) over a certain region and is defined by its observable physical traits (i.e., defined by its lithology, aka rock type).

Question 13

Biostratigraphic unit

Answer 13

A rock unit that can be correlated (mapped) over a certain region and is defined by its fossil content.

Question 14

Define conformable contacts

Answer 14

no significant break (hiatus) in sedimentation has occurred, and the geological record is complete.

Question 15

Define unconformable contacts

Answer 15

a significant break (hiatus) in sedimentation has occurred due to non-deposition or erosion.

Question 16

Three methods of dating the earth

Answer 16

Annual layers on trees, estimation of geological rates, and geometric dating

Question 17

Why does stratigraphy typically require correlation?

Answer 17

a)Because the goal of stratigraphy is to identify large-scale patterns in sedimentary rocks. b)Because outcrops tend to be small and isolated. c)Because proving an event is local or global in extent can help understand how the Earth system operates.

Question 18

List the ages of the rocks from oldest to youngest

Answer 18

C B A D E

Question 19

Define a varve

Answer 19

A sedimentary unit deposited in a year.