1
• A living thing dies and is_____________near quiet water like
________________ and ___________________.
2
• The ____________ ______________of the organism decay
quickly.
3
4
5
• Sediment ______________ ______________
• The layers of mud turn to ____________________ _________.
• The _______________ of the organism are ________________.
What do fossils show?
1. Scientists who ______________ ___ ______________________ are called paleontologists.
2. The fossil record is the combination of all ______________________ gained from _______________around
the world.
3. Paleontologists use fossils to build a _____________________ of past _______________________________.
4. The fossil record:
a. Provides evidence about the history of life and past environments.
1) Fossils found in an area tell whether the area used to be a shallow bay, ocean bottom,
or freshwater swamp.
b. Fossils also provide information about the past _____________________ of an area.
1) Coal, which forms in swamps from plant and animal remains, was found in
___________________.
c. Shows how different groups of organisms have __________________________over time.
1) Evolution: process of ____________________change in ____________________things over long
periods of _________________.
2) Extinct: an organism that _______ _________________ ______________________.
3) Older rock layers contain fossils of ____________________ organisms while younger layers
contain both ____________________ and ________________________organisms.
I.
How old are rock layers?
A. Relative and Absolute age:
1. Relative age: age of rock ________________ to other rocks.
2. Absolute age: number of years that have ________________ since the rock ______________.
3. Geologists use both relative and absolute age since it is often impossible to know the
absolute age of a rock.
II.
III.
IV.
B. Clues to the relative age of rock layers:
1. Law of superposition: in undisturbed horizontal sedimentary rock layers, the
_________________________ layer is on the _____________________.
2. Igneous rocks:
a. An extrusion, lava that has surfaced and cooled, is always ___________________than
the rock below it.
b. An intrusion, magma that has cooled beneath Earth’s surface, is always
_______________ than the rock ___________________and ___________________ it.
3. Faults: A fault is a ____________________in the Earth’s______________________.
a. A fault is always ______________________ than the rock it _____________ through.
4. Index fossils: tell the relative age of the rocks in which they occur.
a. An index fossil is a fossil that is found in ___________________ ______________ and
represent an _____________________ that lived a relatively ________________period of
time.
How can rock layers change?
***The geological record of sedimentary rock is not complete.**
A. Gaps in the geological record are caused by erosion.
1. Erosion can __________ _______________ the younger layers on top (including the fossils).
2. As new layers of sediment form there are ________ (unconformity) in the
__________________record.
B. Folding can _________________________ layers of rock so that the fossils are ______ ___ _________.
Absolute age of rock layers:
A. Radioactive dating: By measuring the rate at which radioactive elements in rocks decay,
geologists can determine the age of the rock.
1. Potassium-Argon dating: useful in dating ancient rocks.
2. Carbon-14 dating: Geologists measure the amount of Carbon-14 left in an
organism’s remains to determine the age of the fossil.
How old is the Earth?
A. Because rocks _______________________ ____________________, geologists cannot use the age of
rocks to determine the age of the Earth.
B. Evolutionists believe Earth formed from ______________, ____________, and _________________left
over after the _________________ formed.
1. Gravity pulled lumps of matter together.
2. The planet may have melted, causing the dense material to sink to the middle and
become the Earth’s ____________________.
3. Less dense material cooled and became the _______________ and________________.
C. Radioactive dating puts the age of Earth’s oldest rocks at 3.8 to 4.28 billion years old.
D. Scientists believe the moon formed from the Earth, so ______________ ________________ can be
used to determine the age of the Earth. (4.6 billion years old). No erosion on the moon.
Geological Time Scale: record of _________ __________________ and the evolution of life
forms as shown in the fossil record.
Dividing Geological Time:
1. Precambrian time:
a. _____________ of Earth’s history
b. Ended ________________ million years ago
2. Eras: long periods
a. Paleozoic
b. _______________________
c. Cenozoic
3. Periods: Era’s are divided into periods
a. Mesozoic era is divided into_______ periods: Triassic, Jurassic, and Cretaceous
How has Earth changed over time?
1. Uniformitarianism: geological _____________________that operate today also operated in the
_______________.
a. ________________________ landforms formed through the same processes observed today.
2. Processes that shape Earth:
a. Natural _________________________ like weathering, erosion, and plate tectonics have
______________________ Earth’s structure.
b. The distribution of land and water on Earth has changed over time.