Sections 2 & 3:
Latitude and
Longitude and Maps
Latitude
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The equator is an imaginary line that circles the Earth
halfway between the north and south poles. It separates
the Earth into two equal halves – the northern
hemisphere and the southern hemisphere.
Latitude is the distance, measured in degrees, north or
south of the equator. These lines are horizontal, parallel,
and never intersect.
The equator is 0 degrees latitude and the poles are 90
degrees latitude.
Locations north and south of the equator are referred to
by degrees north latitude or degrees south latitude. The
degrees are further broken down into minutes and
seconds.
Latitude
Longitude
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The prime meridian is an imaginary line that runs vertically
from the North Pole through Greenwich, England, to the
South Pole. This line separates east from west.
Longitude is the distance east or west of the prime meridian.
These lines are vertical and never intersect, but the lines do
meet at the poles.
Longitude is measured from 0 degrees to 180 degrees. The
prime meridian is 0 degrees longitude. Points east or west of
the prime meridian are referred to by degrees east longitude
or degrees west longitude.
Unlike the equator, the prime meridian does not circle the
Earth. The line of longitude on the opposite side of Earth from
the prime meridian is 180 degrees longitude, call the
International Date Line.
Longitude
Finding Locations
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Latitude is written first in a coordinate set.
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Latitude is given north or south of the equator.
Longitude is given east or west of the prime
meridian.
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Examples: 30degrees N, 90degrees W = New
Orleans, Louisiana
Coordinate Set
Time Zones
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Time is measured by tracking Earth’s movement in relation to
the Sun. Each day has 24 hours, so Earth is divided into 24 time
zones.
Each time zone is 15 degrees of longitude wide and is 1 hour
different from the zones beside it.
The United States has 6 different time zones. As you travel
from east to west across the U.S., you lose an hour. Ex. 5 pm
Eastern Time is 4 pm Central Time is 3 pm Mountain Time is 2
pm Pacific Time.
When you travel across the International Date Line, you gain
or lose a whole day. If you travel west across the International
Date Line, you move forward one day. If you travel east across
the Line, you move back one calendar day. Ex: If you flew from
Hawaii on a Friday, it would be Saturday when you landed in
Australia.
Time Zones of the United States
International Date Line
On the handout find the continent using the
following coordinates
60o N, 140o W :
20oN, 20oW :
20oS, 60oW :
40oS, 140oW :
50oN, 20oW :
80oS, 120oE :
20oS, 20oE :
0o, 80oE :
Maps
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Maps are models of Earth’s surface. The most perfect
map is a globe.
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Maps are made as map projections. A map projection
is made when points and lines on a globe’s surface are
transferred onto paper.
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There are three main types of map projections and all
of them distort the shape of the landmasses of their
areas.
Projections
Mercator Projections
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Mercator map projections are used mainly on
ship.
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They project the correct shape of the
continents, but the areas are distorted.
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Longitude lines are projected as parallel,
making the areas near the poles look much
larger than they are.
Robinson Projections
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A Robinson projection
shows accurate
continent shapes and
more accurate land
areas.
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In this projection, the
lines of longitude are
curved as they are on a
globe, which results in
less distortion near the
poles.
Conic Projection
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Conic projections are
made by projection
points and lines from a
globe onto a cone.
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These are used to make
maps of small area, like
road maps weather
maps.
Topographic Maps
 Topographic maps are detailed maps showing
the elevations of hills and valleys of an area.
• They use lines, symbols, and
colors to represent changes in
elevation
and features on
Earth’s surface.
Each line that shows a different elevation is called a
Contour Line
The spaces between the contour lines are the Contour Interval Not
all contour lines are marked with the elevation. The ones that are
The ones that are labeled are called the index contours. You can
contours. You can determine the elevation of other lines by adding
other lines by adding or subtracting the contour interval from the
contour interval from the elevation on the index contour.
index contour.
Contour Interval
Depression Contour
 This is shown by contour lines with short lines coming
from it hachures (the lines point in the direction of the
depression)
Rules of Topographic Maps
1. They never cross or touch!!!
2. When they are close together, it means that it is a steep
elevation.
3. When they are far apart, it means it is flatter land
4. When the contour lines make a V shape, it means there is
a river
Topographic Maps
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A topographic map shows the changes in elevation of Earth’s surface.
These maps show natural features and also cultural features, such as roads,
cities, and other structures built by people.
These maps are helpful when doing outdoor activities like hiking.
A contour line is a line on topo a map that connects points of equal
elevation.
The difference in elevation between two side-by-side contour lines is the
contour interval, which stays constant throughout a map.
Not all contour lines are marked with the elevation. The ones that are
labeled are called the index contours.You can determine the elevation of
other lines by adding or subtracting the contour interval from the elevation
on the index contour.
Topo Maps
Map Scale
 The
map scale is the relationship between
the distances on the map and distances
on Earth’s surface.
 Example:
A topo map has a scale that
reads 1:80,000. This means that one unit
on the map represents 80,000 units on
land.
Map Legend
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A map legend explains what the symbols used on the map
mean. Examples of map symbols are Roads, Boundaries
between counties, cities, states, buildings, etc
Map Series
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Topo maps are made to cover different amounts of the Earth’s
surface.
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The map series includes maps that measure the same area of
the surface.
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Example: A series may include 7.5 minute maps. These cover
7.5 minutes of latitude by 7.5 minutes of longitude of Earth’s
surface.
100 ft
75 ft
50 ft
25 ft
Side View of my
Mountain
Mountain on a
Topographic Map
The Geologic Time Scale
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It is generally accepted now that Earth is about 4.6 billion
years old.
The Geologic Time Scale
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By studying the characteristics of rocks and the fossils
within them geologists can begin to reconstruct Earth’s
history
The Geologic Time Scale
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Geologic time scale is a record of Earth’s history from 4.6
billion years ago to the present
Geologic Time
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In order to quantify such a vast amount of time Earth’s
long history is divided into specific units.
Geologic Time
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These units are not absolute dates but records that
increase or decrease in relation to each other based on
the rock record and fossil data discovered.
Geologic Time
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The names of the periods do not change, but the years
marking the beginning and ending of each are continually
being refined as more data become available
Eons
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An eon is the largest unit of time and is measured in
billions of years. There are four Eons in Earth’s History.
Eons
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Archean Eon spans 3.8 billion years to 2.5 billion years
B.P.
Eons
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No fossils of any kind
Eons
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Proterozoic Eon spans 2.5 billion years to 540 million
years BP
Eons
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Bacteria-like organisms form, several episodes of
mountain building
Eons
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Phanerozoic Eon spans from 540 million years to present
Eons
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90% OF Earth’s history falls in the Archean and
Proterozoic Eons. This is referred to as Precambrian Time.
Eras
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An era is the next longest span of time. It is measured in
hundreds of millions of years.
Eras
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Eras are defined by differences in life forms found in
rocks. There are three eras in the Phanerozoic Eon
Eras
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Paleozoic Era spans 540-245 million years BP
Eras
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The Paleozoic Era marked the dominance of animal life in
the oceans as plants began to take over the continents
Eras
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Mesozoic Era spans 245-66 million BP
Eras
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The Mesozoic Era marks the dominance of the dinosaurs
on land
Eras
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Cenozoic Era spans 66 million years to present
Eras
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The Cenozoic Era marks the dominance of mammals
Periods
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Periods are defined by the life forms that were abundant
or became extinct at the time in which specific rocks
were deposited. They are measured in tens of millions of
years.
Periods
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The Paleozoic Era has 7 periods
Periods
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Cambrian- 540 MYBP, Marine Invertebrates abundant
Periods
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Ordovician-510 MYBP, First fish appear
Periods
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Silurian- 439 MYBP, First land plants, first insects
Periods
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Devonian- 408 MYBP, First amphibians
Periods
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Mississippian- 362 MYBP, Amphibians dominant
Periods
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Pennsylvanian- 323 MYBP, Reptiles appear
Periods
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Permian- 290 MYBP, Reptiles evolve, coal swamps
Periods
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The Mesozoic Era has 3 periods
Periods
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Triassic Period- 245 MYBP, Mammals appear
Periods
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Jurassic Period- 208 MYBP, Dinosaurs dominant
Periods
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Cretaceous Period- 146 MYBP, Angiosperms appear
Periods
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The Cenozoic Era has 3 periods
Periods
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Paleogene Period-66 MYBP, Early horses
Periods
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Neogene Period- 23 MYBP, Mammals dominant
Periods
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Quaternary Period- 1.6 MYBP, Early Humans appear
Epochs
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The fossil record of the Cenozoic Era is complete enough
to allow further more precise divisions.
Epochs
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The Paleogene Period has three epochs, Paleocene (66),
Eocene (56), and Oligocene (35)
Epochs
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The Neogene period has two epochs, Miocene (23) and
Pliocene (5)
Epochs
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The The Quarternary period has two epochs, Pleistocene
(1.6) and Holocene (0.01)
Clues to the Earth’s Past
Fossils
Paleontologists study fossils and reconstruct the
appearance of animals.
B. Fossils—remains, imprints, or traces of prehistoric
organisms
 1. Fossils can form if the organism is quickly buried by
sediments.
 2. Organisms with hard parts are more likely to become
fossils than organisms with soft parts.
C. Types of preservation
1. Fossils in which spaces inside are
filled with minerals from groundwater
are called permineralized remains.
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2. Carbon film results when a thin film or carbon
residue forms a silhouette of the original organism;
carbonized plant material becomes coal.
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3. Mold—cavity in rock left when the hard parts of an
organism decay
4. If sediments wash into a mold, they can form a cast of
the original organism.
5. Occasionally original remains are
preserved in a material such as amber,
ice, or tar.
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6.Trace fossils evidence of
an organism’s activities
a. Can be footprints left in
mud or sand that became
stone
b. Can be trails or burrows
made by worms and other
animals
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D. Index fossils —abundant, geographically widespread
organisms that existed for relatively short periods of time
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E. Fossils can reveal
information about past land
forms and climate.
F. Most fossils in Virginia are
marine organisms
indicating that the area has
been covered by seawater in
the past.
Relative Ages of Rocks
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A. Principle of superposition—process of reading
undisturbed rock layers
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1. younger
rocks in the
top layers
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2. oldest
rocks in the
bottom layer
B. How old something is in comparison with something
else is its relative age.
 1. The age of
undisturbed rocks
can be determined
by examining layer
sequences.
 2. The age of
disturbed rocks
may have to be
determined by fossils or other clues
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C. Unconformities—gaps in rock layers
1. Angular unconformity—rock layers are tilted and
younger sediment layers are deposited horizontally
on top of the eroded and tilted layers.
 2. A layer of horizontal
rock once exposed and
eroded before younger
rocks formed over it is
called a disconformity.
 3. Nonconformity—
sedimentary rock forms
over eroded metamorphic
or igneous rock.
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D. The same rock
layers can be found
in different
locations; index
fossils can be used
to correlate those
rock layers.
Absolute Ages of Rocks
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A.Absolute age—age, in years, of a rock or other object;
determined by properties of atoms
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B. Unstable isotopes break down into other isotopes
and particles in the process of radioactive decay.
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1. The time it takes for half the atoms in an
isotope to decay is the isotope’s half-life.
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C. Calculating the absolute age of a rock using the ratio
of parent isotope to daughter product and the half-life of
the parent is called radiometric dating.
1. Potassium-argon dating is used to date ancient rocks
millions of years old.
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2. Carbon-14 dating is used to date bones, wood, and
charcoal up to 75,000 years old.
3. Earth is about 4.5 billion years old; the oldest known
rocks are about 3.96 billion years old.
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D. Uniformitarianism—Earth processes occurring
today are similar to those which occurred in the past