UNIT 1: STUDYING EARTH

The study of Earth and the processes and forces that change it, the materials from which it is made, its history, and its place in the universe is called Earth Science.

The four major areas of specialization are:

Astronomy – the study of objects beyond Earth’s atmosphere.

Meteorology – the study of the body of gases that surrounds Earth.

Geology – the study of the materials that make up Earth and the processes that form and change them. 

Oceanography – the study of Earth’s oceans.

EARTH'S SYSTEMS

Earth’s four major systems that are in constant interaction are:

Atmosphere – Layers of gases surrounding the Earth

Hydrosphere – Layer of liquid water between the atmosphere and the upper layer of Earth’s interior

Lithosphere – The layer of rock that forms the solid outer shell at the top of the earth’s interior.

Biosphere – All the organisms on Earth as well as the environments in which they live.

THE ATMOSPHERE

The atmosphere is the body of gases that surrounds the Earth. It extends approx. 560 km (350 miles) from the surface of the Earth.

ORIGIN OF THE ATMOSPHERE

Earth’s early atmosphere was believed to have originated from outgassing by erupting volcanoes.

The volcanoes vented mostly water vapor, carbon dioxide and nitrogen.

Most water vapor ended up in the oceans. Most of the CO2 was absorbed by plants that gave off oxygen and by the oceans.

LAYERS OF THE ATMOSPHERE

Troposphere:

Densest atmospheric layer

Contains most of the mass of the atmosphere

Contains 99% of the water vapor

Water vapor concentration is greatest at equator and lowest near poles

Most weather phenomena take place in troposphere

Temperature decreases as altitude increases

Stratosphere:

Contains much less water vapor

Gases are much less dense

Temperature rises as altitude increases in upper stratosphere

Ozone molecules form the ozone layer in the upper ranges of stratosphere

Mesosphere:

Contains very little ozone

Contains very little water vapor

Temperature decreases as altitude increases

Low density of molecules

Thermosphere:

Gas molecules are widely separated

Very low gas density

Absorption of the most solar radiation

Temperature increases with altitude

EARTH'S SHAPE

Earth is spheroidal (an oblate spheroid): Flattened at the poles and bulging at the equator.

 EVIDENCE OF EARTH'S SHAPE

1. Ships appear to sink below the horizon as they move away from the shore

2. Eclipses (The earth throws a circular shadow on the moon during a lunar eclipse)

3. Photographs taken from space

4. Measurements of Gravity – The similarity of the strength of gravity at sea level all over the Earth’s surface. (If the earth were flat, the force of gravity would slant obliquely towards its center of gravity as one moved towards the edges )

5. Observations of the altitude of Polaris – the North Star (when traveling northward, stars such as Polaris, the north star, are higher in the sky)

EARTH'S MEASUREMENTS

Polar Diameter: 12,714 km

Equatorial Diameter: 12,756 km

Average Diameter: 12,735 km

Polar Circumference: 40,008 km

Equatorial Circumference: 40076 km

THE METRIC TABLE

Length

10 millimeters (mm) =  1centimeter (cm)

10 cm = 1 decimeter (dm) 

100 cm = 1 meter (m)

1000 m = 1 kilometer (km)

Mass

1000 micrograms (mcg) = 1 milligram (mg)

1000 mg = 1 gram (g)

1000g = 1 kilogram (kg)

Volume

1 milliliter (ml) = 1 cubic centimeter (cm3)

1000 ml = 1 liter (L)

 ADDITIONAL INFORMATION

When converting a larger unit to a smaller unit, the decimal moves to the right.

When converting a smaller unit to a larger unit, the decimal moves to the left.

One inch = 2.54 cm

One m = 39.4 inches

One km = 0.62 miles

UNITS OF MEASUREMENT IN EARTH SCIENCE

Length- the meter (m)is the standard unit of length (measured with a ruler).

Mass – the amount of matter in a object [measured with a balance in units called milligrams (mg), grams (g), kilograms (kg), etc.].

Area  - the amount of surface included within a set of boundaries and is expressed in square units of length (for example, cm2, m2, km2).

Volume – the amount of space an object occupies (measured in ml, cm3, m3, km3, etc.).

Density – the amount of matter that occupies a given area (D = M/V). Units are in g/cm3 or g/ml.

Normally, solids are denser than liquids, and gases are the least dense (ice is an exception to this rule).

Any object with a density less than 1 g/cm3 will float when placed in water.

The same substance will have the same density value regardless of its size.

When the volume of a gas increases due to an increase in temperature or a decrease in pressure, the density will decrease.

Rate of Change – Change in value per unit of time (change in value divided by time).

To solve a rate of change problem from a graph, choose 2 different positions along the Time axis (x-axis) and from these positions move directly up until the intersection with the graph line.

Read over to the y-axis to obtain their values.

Subtracting these two values, will give the “change in value.” Use the time difference you selected, substitute into the equation and solve for the rate of change.

 LOCATING POSITIONS ON EARTH

The latitude-longitude coordinate system is commonly used to locate points on Earth. Latitude & longitude are measured in angular units:

Degrees (o)

Minutes (‘) 

Seconds (”)

60 minutes equal 1 degree

60 seconds equal 1 minute

Latitude lines (called parallels) run in an East-West direction

Longitude lines (called Meridians) run in a North-South direction

MEASURING LATITUDE

The latitude of a point on Earth’s surface is its angular distance North or South of the equator.

The fixed reference point for latitude is the equator – zero degrees latitude

Each degree of latitude is equivalent to about 111km on Earth’s surface (circumference divided by 360 degrees – 40,000 km/ 360 = 111 km)

Each minute of latitude is 1.85 km (111 km divided by 60)

The highest degrees of latitude are 90 degrees N at the North Pole and 90 degrees S at the South Pole.

MEASURING LONDITUDE

Longitude is the angular distance east or west of the Prime Meridian, the meridian of zero degrees longitude.

The highest degree of longitude east or west of the Prime Meridian is 180 degrees (the International date Line).

Since Earth makes one complete rotation in 24 hours, in one hour, Earth rotates 15 degrees (360/24).

The 180th meridian, the International Date Line, is half the distance around the Earth.

The half of the world that is west of the prime meridian has west longitude.

The half of the world that is east of the prime meridian has east longitude.

TIME ZONES

Earth is divided into 24 time zones (it takes 24 hrs to complete one rotation). Since Earth rotates at 15 degrees per hour, each time zone is 15 degrees wide.

There are 6 different time zones in the United States.

Each time you travel through a time zone you gain or lose time.

The International Date Line or the 180-degree meridian is the transition line for calendar days.

If you were traveling west across the International Date Line, you would advance your calendar one day.

If you were traveling east, you would move you calendar back one day.

TERRESTRIAL NAVIGATION

Navigation is the science of identifying your position on Earth.

The latitude of any location north of the equator is almost equal to the angle of Polaris (the North Star’s altitude) above the horizon.

In the southern hemisphere, early navigators used the Southern Cross as their points of reference.

DETERMINING THE LONGITUDE OF A POINT

First determine the time at the prime meridian (Greenwich) when it is solar noon at your location (local clock time).

Find the time difference, in hours, between local clock time and Greenwich (location of the prime meridian in England) Time.

Your longitude will be this time difference multiplied by 15 degrees (the rate of Earth's rotation per hour).

If local time is earlier than Greenwich Time, your position is west of the prime meridian or west longitude.

If local time is later than Greenwich Time, your position is east of the prime meridian or east longitude.

FIELD MAPS

A field map is a region of space that has a measurable quantity at every point (for example, temperature, pressure, magnetism, gravity, and elevation).

Isolines connect points of equal field value.

Gradient is the rate at which a field value changes.

Contour Lines are isolines that connect points of equal elevation.

RULES FOR DRAWING ISOLINES

1. Isolines connect points of equal value

2. Isolines are gentle, curving lines - no sharp corners

3. Isolines are always closed curves even though the map might only show part of it

4. Isolines NEVER cross - this would mean that one point has two different values

5. Isolines usually are parallel

A steep (high) gradient changes quickly and the isolines are close together.

A gentle (low) gradient changes slowly and the lines are far apart.

MAP SYMBOLS

Surface features on topographic maps are represented by map symbols.

Brown for contour lines

Black & red for human-made structures

Blue for bodies of water

Green for woods or areas with trees

CONVENTIONS USED IN TOPOGRAPHIC MAPS

All points on a contour line have the same elevation.

Every fifth line, called an index line, is generally thicker and indicated in black ink and labeled with the line’s elevation.

All contour lines are closed, but they may run off the map.

To determine a contour interval, find the difference in elevation between two adjacent index contours; count the number of contour lines from one index contour to the next, not including the first contour line. Then divide the difference by the number of contour lines.

Two contour lines of different elevations may not cross each other.

Contour lines may merge at a cliff or waterfall.

The spacing of contour lines indicates the nature of the slope. The closer the lines are spaced, the steeper the slope.

Where contour lines cross a stream, they always form a V whose apex points up the valley.

Where contour lines cross a ridge between valleys, they often form a V whose apex points down the valleys.

 MAP SCALES

A map scale is the ratio between the distance shown on a map and the actual distance on the ground.

Map scales can be expressed in three ways: Verbally, Fractionally, and Graphically

Verbally, such as one inch equals one mile.

Fractionally, such as 1/500,000 or 1:500,000

The graphic scale is printed so that each unit is precisely the correct size for the distance indicated.

The graphic scale can be used as a ruler to measure distances on the map.

MAP DIRECTIONS

The convention used in most topographic maps is that the top of the map is north. However, since north is determined with a compass, and geographic north differs from magnetic north, most topographic maps include an arrow (compass rose) pointing north.

MAP PROFILES

A map profile shows what a cross section of land looks like between two points:

The two points between which the profile is to be drawn are chosen, and a line is drawn to connect them.

The edge of a piece of paper is placed along the line, and the edge of the paper is marked wherever it intersects a contour line.

The paper is moved to a piece of graph paper on which a vertical scale has been marked to match the contour lines intersected.

At each point where a contour crosses the edge of the paper, a line of the appropriate height is drawn on the graph paper

The endpoints of the lines are connected in a smooth line to form the finished profile