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Views of the Earth's Past
Chapter 4 The Changing Earth, Fossils/Geologic Time
39
Science
7th Grade
03/15/2010

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Term
fossils
Definition
These are traces or remains of living things from long ago.
Term
hardened animal remains
Definition
Most fossils are made of these.
Term
original remains
Definition
These are fossils that are the actual bodies or parts of organisms.
Term
Siberia and Alaska
Definition
These are two locations where 10,000 year old mammoths have been found preserved in ice.
Term
tree resin (sap)
Definition
Amber, which preserves small insects, is hardened ____________________.
Term
La Brea tar pits
Definition
This is one of the world's most famous fossil locations.
Term
sedimentary
Definition
Fossils form mostly in this type of rock.
Term
mold
Definition
An organism dies and falls into soft sediment. Eventually, the sediment becomes rock and the organism decays. This is the process of ____________________ formation.
Term
casts
Definition
These are made when minerals fill molds.
Term
trace fossils
Definition
Examples of these would be footprints, trails, holes and scat.
Term
chicken
Definition
T-Rex was a slow runner. What modern animal did scientists build a model of to gain this information?
Term
ice cores and tree rings
Definition
Name two things that scientists analyze to study past weather patterns.
Term
petrified wood
Definition
This is a stone fossil of a tree
Term
relative age
Definition
This is the age of an object in comparison with other objects.
Term
horizontal
Definition
Over time, sedimentary rocks form ____________________ layers.
Term
bottom
Definition
In sedimentary layers, where is the oldest rock?
Term
igneous rock
Definition
What other type of rock could cause sedimentary rock to become disturbed?
Term
plutons
Definition
These are large bodies of igneous rock that form when magma is injected into surrounding rock, then cools.
Term
index fossils
Definition
These are fossils of organisms that were common, widespread, and that lived in a particular span of time.
Term
marine organisms
Definition
The most useful index fossils are of what type of organism?
Term
nautilus, brachiopod, cephalopod
Definition
Name three organisms that provide us with useful index fossils.
Term
absolute age
Definition
This is the actual age of an event or an object.
Term
radioactivity
Definition
Atoms of an unstable element break down into a stable form. What is this called?
Term
half-life
Definition
This is defined as the length of time it takes for half of the atoms in a sample of an unstable element to change into a stable form.
Term
carbon
Definition
Since this element is a part of every living thing, we use it in radioactive dating.
Term
They are made of many different types of rocks.
Definition
This is why we cannot use radioactive dating on sedimentary rocks.
Term
James Hutton
Definition
He was the Scottish scientist who first hypothesized that the Earth was always changing.
Term
uniformitarianism
Definition
Hutton's theory, states that the same forces that changed the Earth in the past are still changing the Earth today.
Term
Geologic Time Scale
Definition
This divides the Earth's history into intervals of time defined by major events or changes.
Term
100,000 years
Definition
Fossil evidence shows that humans have been around for how many years?
Term
eon
Definition
This is the largest unit of geologic time.
Term
90%
Definition
The Hadean, Archaen, and Proterozoic eons are called Precambrian time and make up how much of Earth's history?
Term
single-celled organisms
Definition
Life in Precambrian time consisted mostly of these.
Term
Paleozoic Era
Definition
Pangaea formed in this era.
Term
Mesozoic Era
Definition
The dinosaurs ruled the Earth in this era.
Term
Cenozoic
Definition
"The Age of Mammals"
Term
The Quaternary period
Definition
Fossils of the first humans were found in this time.
Term
4,600,000,000 years
Definition
Through radioactive dating, scientists know that the Earth is how old?
Term
3.8 billion years
Definition
The oldest evidence of life on Earth comes from fossils dating back this long.
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