Geological time

Question 1

What does deep time tell us?

Answer 1

Discovery of the antiquity of the Earth is the most important discovery that the science of geology has made (Earth = ~4.6 billion years)

Question 2

Define archbishop Ussher:

Answer 2

analyzed biblical scriptures and studied genealogies to calculate the age of the Earth (~6 thousand years)

Question 3

Define relative geological ages:

Answer 3

great for sedimentary rock; based upon order of formation. Determination of older vs. younger relationships.

Question 4

9 Principles of geology:

Answer 4

1. Principle of uniformism
2. superposition
3. lateral continuity
4. cross-cutting relationship
5. baked contacts
6. inclusions
7. fossil succession
8. unconformities

Question 5

Principle of uniformism:

Answer 5

developed by James Hutton in the Scottish highlands. The present is the key to the past!!

Question 6

Superposition:

Answer 6

In an undisturbed succession of sedimentary rock layers, the oldest layer is at the bottom and the youngest layer is at the top.

Question 7

Original horizontal:

Answer 7

Sediments settle out by gravity. This causes sediments to accumulate horizontally. So, tilted sedimentary rocks must be deformed.

Question 8

Lateral continuity:

Answer 8

Sedimentary layers usually accumulate in continuous sheets in a given region. They will be continuous either until they pinch out at their margins or are cut (by a river, stream, etc.)

Question 9

Cross-cutting relations:

Answer 9

Younger features truncate (cut across) older features. Faults, dikes, erosion, etc., must be younger than the material that is faulted, intruded, or eroded.

Question 10

Baked contacts:

Answer 10

An igneous intrusion will bake or metamorphose the surrounding rocks.

Question 11

Inclusions:

Answer 11

Where a rock fragment is found within another. Inclusions are always older than the rock they are in.

Question 12

Fossil Succession:

Answer 12

Fossils are often preserved in sedimentary rocks. Fossils indicate past depositional environments and correlate strata. Specific fossils are only found within a limited time range (Index Fossils).

Question 13

Unconformities:

Answer 13

represents a gap in time from non-deposition or erosion

Question 14

Angular unconformity:

Answer 14

Rocks below this unconformity were tilted or folded before the unconformity developed

Question 15

Nonconformity:

Answer 15

igneous/metamorphic rocks overlain by sedimentary rocks.

Question 16

Disconformities:

Answer 16

occur between parallel layers of sedimentary rocks.