1. The Rock and Fossil Record
Studying the rock and fossil record helps us understand Earth’s history and the history of
life on Earth.
The Principle of Superposition (Law of Superposition)
Which layer is the oldest?
In _________________rock, the oldest is on the bottom the youngest in on the
top, this is Superposition. The rock’s age is based on the position of the rock.
Applies mainly to ____________________________________!
This principle states that the ___________ rocks are located above the _________
rocks. The rock layer must be _____________!
Disturbing Forces
Forces within Earth can disturb the rock layers (rock layers are also known as
_______________________).
Examples of Events (plate boundaries converging, diverging, transforming)
1. ______________ 2. _________________
Examples of Features that Disturb:
1. _____________ (found along all plate boundaries)
2. ______________ (potential volcanic activity)
Unconformities: An unconformity is a gap in the ____________________ that can occur
when erosion wears away rock layers and other rock layers form on top of the eroded
surface. (Just remember these are usually as a result of erosion and nondeposition.)
The Geologic Column
Simply think of the _______________________________
An _________________ of ___________________ in which the oldest rock layers
are at the ____________
Dating Rock Layers
2 Ways to Measure the Age of Rocks:
1.
2.

2. Relative Age
The _______________________ of a rock is its age compared to other rocks.
Use words like: “older or younger”
Now you do an example of relative age!! _____________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
“When Igneous Rock Meets Sedimentary Rock”
o REMEMBER: Igneous Rock
 Lava that cools at the surface is called an_____________. Rock below an
extrusion is always _______________.
 Magma that cools beneath the surface is called an_____________. An
intrusion is always ________________ than the rock layers around.
Absolute Age
The _________________________ of a rock is the number of years since the rock
was formed.
Fossils
Why is the study of fossils so important? _______________________________
The Beartooth Range of Montana is just north of Yellowstone. In this location you will
find Beartooth Butte. Partway down from its 10,500 foot (3200 m) summit, within the
dark red zone of rocks, geologists have found fish fossils as old as 400 million years.
How is this possible? ____________________________________________
_____________________________________________________________
____________________________________________________________
(Plate tectonics push up the rock making a mountain, weathering and erosion
move the dirt and expose the marine fossil.)
_______________can give us clues of what Earth’s surface looked like in the past.
Fast Fossil Facts
Fossils are the ______________________________________________ on Earth.
Why are all dead organisms not preserved as fossils?
1. ____________________________________________________________
____________________________________________________________
2. ___________________________________________________________
_____________________________________________________________

3. o (When an organism dies, its soft parts often decay quickly leaving only the hard
parts to fossilize.) Examples: ____________________________________
1) Fossils provide clues to the past
o Fossils give clues of ___________________ and ____________________.
 Examples:
1. Fossils of palm leaves in Antarctica could mean that Antarctica was once
in a warm tropical area. (______________________)
2. Marine fossils found on mountain tops or land well above sea level.
(____________________________)
2) Revisiting the Rock Cycle (Fossil Facts)
1. Fossils are generally most abundant in marine __________________________.
2. Fossils generally are not found in ____________________________________.
3. Most fossils found in __________________________________.
Fossil Types
1. ________________: provide evidence of the activities of ancient organisms.
Examples: ___________________, animal trails, or animal burrows.
2. _____________: a hollow area in sediment in the shape of an organism or part of an
organism.
3. _____________: a copy of the shape of an organism.
Other Types
4. _______________________: fossils in which minerals replace all or part of the
organism. Ex: petrified wood
5. ______________________: an extremely thin coating of carbon on rock that forms
when materials that make up an organism become gases and escape leaving only carbon
behind.
6. _____________________: formed when an organism is preserved with little or no
change. {For example when organisms become preserved in tar, amber (tree sap), and
freezing.}
Index Fossils
An____________________ must be widely distributed and represent a type of organism
that existed only briefly.
One example of an index fossil is a _______________.
Trilobites were a group of hard-shelled animals whose bodies had three distinct
parts.They evolved in shallow seas more than 500 million years ago.