Ch. 11 (Kaitlin)

Question 1

PRINCIPLE OF SUPERPOSITION

Answer 1

the principle that in any undeformed sequence of sedimentary rocks, each bed is older than the layers above and younger than the layers below.

Super =ABOVE
Positum =TO PLACE

Question 2

ORIGINAL HORIZONTALITY

Answer 2

layers of sediments are generally deposited in a horizontal or nearly horizontal position.

if we observe rocks as flat, they have not been disturbed and still have their original horizontality.

Question 3

LAW OF CROSS CUTTING

Answer 3

a principle of relative dating which says that a rock or fault is younger than any rock or fault through which is cuts.

Question 4

What are the three different unconformities?

Answer 4

1. ANGULAR UNCONFORMITY
2. DISCONFORMITY
3. NON-CONFORMITY

Question 5

EXPLAIN THE DIFFERENCE BETWEEN THE THREE DIFFERENT UNCONFORMITIES

Answer 5

1. ANGULAR UNCONFORMITY
   - the strata below dip at an angle different from that of the beds above
   - PERIOD OF EROSION DURING A PAUSE OF DEPOSITION
2. DISCONFORMITY
   - a type of unconformity in which the beds above and below are PARALLEL.
   - PERIOD OF EROSION RATHER THAN DEPOSITION
3. NON-CONFORMITY
   - older metamorphic or intrusive igneous rocks are overlain by younger sedimentary strata.
   - PERIOD OF UPLIFT AND EROSION OF OVERLYING ROCKS

Question 6

WHAT ARE INDEX FOSSILS AND HOW DO THEY HELP AGE DATE SEDIMENTARY STRATA?

Answer 6

A fossil that is associated with a particular span of geologic time.

They are examined and used to correlate rocks of similar age in different regions.

Question 7

FOSSIL ASSEMBLAGE

Answer 7

the overlapping ranges of a group of fossils collected from a layer.

Examining an assemblage allows the age of the sedimentary layer to be established.

Question 8

PRINCIPLE OF LATERAL CONTINUITY

Answer 8

sedimentary beds originate as continuous layers that extend in all directions until they grade into a different type of sediment or thin out at the edge of a sedimentary basin.

EXAMPLE:
IMAGINE A CANYON. CANYONS ARE FORMED FROM ERODED LAYERS OF ROCK. LATERAL CONTINUITY SHOWS US THAT THE LARGE CANYON THAT HAS FORMED AND THE NOW SEPARATED ROCK LAYERS WERE ACTUALLY ONCE CONTINUOS LAYERS ACROSS THE EMPTY SPACE AND THERE WAS PREVIOUSLY NO CANYON.

Question 9

RADIOACTIVE DECAY

Answer 9

the spontaneous decay of certain unstable atomic nuclei

Question 10

RADIOMETRIC DATING

Answer 10

the procedure of calculating the absolute ages of rocks and minerals that contain radioactive isotopes

Question 11

HALF LIFE

Answer 11

the time required for one-half of the atoms of a radioactive substance to decay

Question 12

BE ABLE TO CALCULATE THE AGE OF A ROCK SAMPLE USING THE HALF LIFE METHOD

Answer 12

WHEN THE QUANTITIES OF PARENT AND DAUGHTER ARE EQUAL (Ratio 1:1), ONE HALF LIFE HAS OCCURRED.

If the age of the RADIOACTIVE ISOTOPE is known and the PARENT/DAUGHTER RATIO can be determined, the age of the sample can be determined.

If the half life is 1 million years and the parent daughter ratio is 1:15, the sample must be 4 million years old.

I am confused on this concept but look on page 362 of the book.