Geology 3

Question 1

Why aren’t fossils found in other rocks

Answer 1

The other 2

rock types the fossils would be destroyed.

Question 2

Index fossils are from

Answer 2

• animals that were common
• lived over a very large area
• existed as a species for a short time.

Question 3

Index fossils allow scientists

Answer 3

to quickly estimate the age of a rock layer.

Question 4

Trilobites once _______ the sea floor, but are now ___________.

Answer 4

Dominated, extinct

Question 5

Reltative age –

Answer 5

doesn’t give a number, just describes how old one thing is compared to another.

Question 6

Absolute age –

Answer 6

Scientists study the radioactive chemicals in rocks to determine their actual age in years.

Question 7

Absolute age only works with

Answer 7

Igneous rocks

Question 8

Geologists estimate the age of the Earth to be

Answer 8

4.6 billion years

Question 9

glaciers form when

Answer 9

more snow falls on an area than melts for a period of hundreds
or thousands of years.

Question 10

Fossils are most commonly found in

Answer 10

sedimentary rock

Question 11

Drumlins point in the direction

Answer 11

the glacier was moving:

Question 12

Kettle lakes formed when

Answer 12

giant blocks of ice were buried, melted, then the ground collapsed into the water forming a lake

Question 13

Glacial Erratics are

Answer 13

large boulders that a glacier dropped far from where the rock originally formed.

Question 14

Lake Agassiz was

Answer 14

• the huge lake filled with glacier melt water • covered south-­‐central Canada and the
Northwestern part of Minnesota.

Question 15

Water flowing South out of Lake Agassiz as the

Answer 15

giant glacial River Warren.

Question 16

River Warren carved

Answer 16

the valley

that the Minnesota River now occupies.

Question 17

Potholes drilled by rocks in ________ can be found in ________

Answer 17

Whirlpools

Taylor’s Falls

Question 18

There is a ___________________ in Brown’s Valley in Western Minnesota.

Answer 18

continental divide

Question 19

All the water north of here flows

north through

Answer 19

the Red River to Hudson Bay

Question 20

all the water south of here flows down the

Answer 20

Minnesota River to
the Mississippi River to
the Gulf of Mexico.

Question 21

Fossils are

Answer 21

the preserved remains

and traces of an organism.

Question 22

What parts are more likely to get preserved (fossils)

Answer 22

Harder parts like

Bones 
Teeth 
Horns and antlers 
Shells 
Wood 
Seed pods

Question 23

Mold/Cast -­‐

Answer 23

Organism gets buried, then rots away
leaving a hole = mold. Later, minerals fill
the hole and make a 3D copy = cast.

Question 24

Petrified –

Answer 24

Silica rich water soaks into bone or wood
and replaces most of the original material.

Common Examples: Wood, Bones

Question 25

Carbon Film –

Answer 25

The enOre organism decays away and leaves behind a thin film of dark carbon. Looks like a photocopy or ink print. Common Examples: leaves, fish

Question 26

Preserved Remains–

Answer 26

Plant or animal material gets trapped and preserved in tar, amber (tree sap) or ice. Common Examples: insects in amber, mammoth in ice, mammals in tar pits

Question 27

Trace Fossils –

Answer 27

``` Not actual part of an organism, but evidence that it was there. Common Examples: Footprints, Burrows, Coprolites (poop), Gastroliths (stomach stones) ```

Question 28

Mold/Cast Examples

Answer 28

Shells & Fish

Question 29

Relative dating –

Answer 29

tells which layer is oldest, 2nd oldest, so on.

Question 30

The Law of Superposition:

Answer 30

As you go down, rock layers get older. An intrusion of rock is younger than the layers it intrudes into.

Question 31

Absolute Dating –

Answer 31

Radioactive elements break down at very predictable rates. By determining the percentage of radioactive element left in a rock, the age can be closely estimated

Question 32

Index Fossil –

Answer 32

A special fossil that can be used to closely estimate the age of a layer of rock

Question 33

In order to form a useful index fossil,

Answer 33

an animal must be easily preserved, widely spread over earth, and live for a short period of time.

Question 34

What 3 characteristics make an organism a good index fossil?

Answer 34

1. Easily Preserved 2. Very Common/Widespread 3. Lived for a short period of time

Question 35

Why are index fossils important?

Answer 35

Allow geologists to quickly estimate the age of a rock layer

Question 36

Which rock type works best for radioactive dating?

Answer 36

Igneous

Question 37

In which rock type do most fossils form?

Answer 37

Sedimentary

Question 38

Till

Answer 38

ground up rock, jumble of material. | ^ Very poorly sorted, large & small, moves then drops when glacier melts

Question 39

Esker

Answer 39

snake looking thing hills | ^ as a glacier is melting, the water goes down and flows under it creating a cave

Question 40

Kame

Answer 40

flat then horn/cone shaped hill | ^ when a depression in the surface of a glacier fills with sediment

Question 41

Erratics

Answer 41

large boulders plopped down by a glacier in an random place | ^ when glacier melts

Question 42

Potholes

Answer 42

when the glaciers were melting- formed from whirlpool spinning rocks that acted like drillbits

Question 43

Giant lake that formed from meltwater-

Answer 43

Lake Agassiz

Question 44

Browns Valley

Answer 44

continental divide- means separates water sheds | Goes 2 ways

Question 45

What do we call the big scratches glaciers make in rocks?

Answer 45

Sirations