Notes: A Trip Through Geologic Time
A.
B.
C.
pg. 95
Fossils are the preserved remains or traces of living things
1.
Form when living things die and are slowly buried by sediments that slowly harden into rock and
preserve the shapes of the organisms
2.
Usually found in sedimentary rocks
3.
Kinds of Fossils
a.
Petrified Fossils – minerals replace all or part of an organism; “turn it to stone”
b.
Molds and Casts – most common
1.)
mold – a hollow area in the sediment in the shape of an organism
2.)
cast – a copy of the shape of an organism if minerals and sediment seep into the
empty space of a mold
c.
Carbon Films – a thin coating of carbon on rock
d.
Trace Fossils – provide evidence of the activities of ancient organisms, ex: footprints
e.
Preserved Remains – some processes preserve remains with little or no change, ex: tar,
amber, freezing
4.
The Fossil Record – provides evidence about the history of life on Earth; shows how different
groups of organisms have changed over time
Age of Rocks
1.
Relative Age of rock is its age compared to the ages of other rocks
a.
law of superposition – oldest layer is at the bottom and each higher layer is younger than
the layers below
2.
Absolute Age of a rock is the number of years since the rock formed
a.
radioactive dating – during radioactive decay, the atoms of one element decay into
atoms of another element
b.
This shows the age of the oldest moon rocks, so scientists infer that the Earth is a little
older than those rocks – about 4.6 billion years old
The Geologic Timeline – a record of the life forms and geologic events in Earth’s history
1.
Precambrian Time – where geologic time begins, covers about 88% of Earth’s history,
ended 544 million years ago
2.
Eras – the time between Precambrian and the present are divided into three long units
a.
Paleozoic – began about 544 million years ago and lasted 300 million years;
many animals were invertebrates (no backbone) in this era; “paloe-“ means
ancient or early and “-zoic” means life
b.
Mesozoic – began about 245 million years ago and lasted about 180 million
years; the Age of the Dinosaurs and mammals began to evolve; “meso-“ means
middle
c.
Cenozoic – most recent era; began about 65 million years ago and continues to
present day; the Age of Mammals; “ceno-“ means recent
3.
Periods – these are subdivided eras and are characterized by what life existed worldwide
4.
Epochs – further subdivided periods of the Cenozoic Era because the fossil record of this
era is more complete and there are a lot more events to place in sequence.
Notes: A Trip Through Geologic Time
A.
B.
C.
pg. 95
Fossils ____________________________________________________________________________
1.
Form when __________________________ and are slowly _____________________________
that slowly _________________________ and _________________________ of the organisms
2.
Usually found in __________________________________
3.
Kinds of Fossils
a.
Petrified Fossils – _________________________________________; “turn it to stone”
b.
Molds and Casts – __________________________
1.)
mold – a _________________ in the sediment in the _______________________
2.)
cast – a _____________________________________ if minerals and _________
_______________________________________ of a mold
c.
Carbon Films – a __________________________________ on rock
d.
Trace Fossils – provide _______________________ of ancient organisms, ex: footprints
e.
Preserved Remains – some processes ________________________________________,
ex: tar, amber, freezing
4.
The Fossil Record – provides evidence about ________________________________________;
______________________________________________________________________________
Age of Rocks
1.
Relative Age of rock is its ________________________________________________________
a.
law of superposition – ____________________________________________________
________________________________________________________________________
2.
Absolute Age of a rock is ________________________________________________________
a.
radioactive dating – during radioactive decay, the _____________________________
________________________________________________________________________
b.
This shows the age of ____________________________, so scientists infer that the
Earth is a little older than those rocks – _______________________________________
The Geologic Timeline – ______________________________________________________________
1.
Precambrian Time – where _______________________________, covers about _____
_____________________________, ended 544 million years ago
2.
Eras – the _____________________________________ are divided into ____ long units
a.
Paleozoic – began about 544 million years ago and lasted 300 million years;
____________________________________________ in this era; “paloe”- means
________________________ and “-zoic” means ______________
b.
Mesozoic – began about 245 million years ago and lasted about 180 million
years; the ___________________________ and ___________________ began to
evolve; “meso”- means __________________
c.
Cenozoic – __________________________; began about 65 million years ago
and _________________________; the ____________________________;
“ceno”- means __________________
3.
Periods – these are _____________________ and are characterized by ______________
___________________________________________
4.
Epochs – _______________________________________ because the ______________
of this era _____________________ and there are a lot more events to place in sequence.
Paleontologist- scientists who study fossils
Evolution- the change in living things over time
Extinct- if an organism no longer exists and will never again live on Earth
Extrusion- lava that hardens on the surface and forms igneous rock; it is always younger than the rock
below it
Intrusion- magma that pushes into bodies of rock below the surface and hardens; it is always younger
than the rock layers around and beneath it
Fault- a break in Earth’s crust; it is always younger then the rock it cuts through
Index Fossil- used to help geologists match rock layers; must be widely distributed and represent an
organism that existed for a geologically short period of time
Unconformity- a gap in the geologic record; it shows where rock layers have been lost due to erosion
Radioactive decay- the atoms of one element break down to form atoms of another element
Half-life- the time it takes for half of the radioactive atoms to decay; the rate of decay of each
radioactive element never changes
Comet- a ball of gas, dust, and ice that orbits the sun
Invertebrate- animals without backbones (jellyfish, worms)
Vertebrate- animal with a backbone
Amphibian- an animal that lives part of its life on land and part of its life in water
Reptile- have scaly skin and lay eggs that have tough, leathery shells
Mass Extinction- many types of living things become extinct at the same time
Mammal-