H. Williams GEOG. 1710 EARTH SCIENCE
EXAM
1 REVIEW SHEET
Key
words/concepts:
Earth
science (Note: only the section entitled "What's the "Science" in
Earth Science?" will be included on Exam 1 - the rest of the material will be included on Exam 3) is part of physical
geography - a subject focusing on SPATIAL aspects of physical features (e.g.
what is the pattern of rainfall in this state?) and processes (what processes
create this rainfall pattern?) of the earth's surface. The course is concerned
with interactions of the LITHOSPHERE (rock), ATMOSPHERE (air), HYDROSPHERE
(water), and BIOSPHERE (living things).
PORTRAYING
THE EARTH: LATITUDE AND LONGITUDE; TOPOGRAPHIC MAPS:
The
Earth rotates about the axis of rotation, which connects the north and south
poles; the plane of the equator is midway between the poles and at right angles
to the axis. Lines connecting the poles run north-south and are called
MERIDIANS or lines of LONGITUDE; lines running parallel to the equator run
east-west and are called PARALLELS or lines of LATITUDE. Latitude is measured
by the angle from the Earth's center north or south from the plane of the
equator. Longitude is measured by the angle from the Earth's center east or
west from the Prime Meridian running through Greenwich, England (Prime Meridian
= 00). To increase accuracy, degrees of latitude and longitude are
divided into minutes - a 60th of a degree, and seconds - a 60th of a minute. It
should be noted that because longitude lines converge, the distance of 1 degree
of longitude changes with latitude; i.e. at the Equator, 1 degree of longitude
= 40 000 km/3600 = 111 km; 1 minute = 1.85 km; 1 second = 30 m. At
600 N, 1 degree of longitude = 20 088 km/3600 = 55.8 km;
1 minute = 0.93 km; 1 second = 15.5 m. Unlike longitude lines, latitude lines
do not converge. One minute of latitude defines the NAUTICAL MILE (1.85 km) and
the KNOT (1 nautical mile per hour). The scale of a map is the ratio of map
distance to true distance; shown by a Graphic Scale or Representative Fraction
(RF). In the U.S., the most common map is the United States Geological Survey
7.5 minute quadrangle. These have an RF of 1:24000 (approximately 2.64 inches
to a mile) and cover an area 7.5 minutes of longitude wide and 7.5 minutes of
latitude long. Topographic maps show height by using contour lines, spot
heights and bench marks. Contours appear on USGS maps as fine brown lines, with
every fifth contour (called index contours) thickened. The contour interval is
the vertical height difference between adjacent contours.
GIS:
Geographic Information Systems combine computer-based mapping and analysis.
Usually map features are stored in layers in the computer and can be
superimposed on screen. The utility of GIS is the ability to manipulate and
analyze very large amounts of spatial (map) data very quickly.
EARTH-SUN
RELATIONSHIPS; SEASONS:
The
earth rotates on its axis in 24 hours and revolves around the Sun in 365.25
days within the plane of the ECLIPTIC; the earth is closer to the Sun at
PERIHELION on January 3rd, and furthest from the Sun at APHELION on July 4th.
The Earth's axis is tilted 23.50 from the perpendicular (or 66.50
from the plane of the ecliptic). The tilt of the earth determines the angle at
which the sun's rays (incoming solar radiation or insolation) strike the
surface; the steeper the angle, the more the Sun's rays are concentrated and
the more heating occurs - this changes throughout the year and is the cause of
SEASONS. Due to this tilt, the latitude where the noon rays of the Sun are
perpendicular to the surface changes throughout the year; the northernmost
latitude reached by the perpendicular rays of the Sun is 23.50 north
on about June 21st: this latitude is defined as the TROPIC OF CANCER; the
southernmost latitude reached by the perpendicular rays of the Sun is 23.50
south on about December 21st: this latitude is defined as the TROPIC OF
CAPRICORN. From the point of view of the northern hemisphere, June 21st and
December 21st are the summer and winter SOLSTICE, respectively. It should also
be noted that during summer solstice, poleward of 66.50 north
receives continuous sunshine - so the day is 24 hours long; poleward of 66.50
south receives no sunshine - so the night is 24 hours long. This is how the
ARCTIC CIRCLE and the ANTARCTIC CIRCLE are defined. The circle of illumination
only passes through the poles midway between the solstices, in March and
September. These times are the EQUINOXES - Spring equinox on about March 20th,
Autumnal Equinox on about September 22nd. Figure 2-15 in the text is a good
illustration of seasonal changes in insolation and the position of the circle
of illumination.
INTRODUCTION
TO THE ATMOSPHERE:
The
atmosphere is a mixture of gases, solids and liquids.
Gases:
Nitrogen, Oxygen and Argon: Nitrogen (78.1%), oxygen (20.9%) and argon (0.9%).
Water Vapor (0-4%- it varies). Carbon Dioxide (0.0353%). Ozone (< 2ppm) is
concentrated in a layer 9 - 30 miles above the surface. Ozone absorbs
ultraviolet radiation from the Sun. Pollutant Gases (very small amounts), e.g.
carbon monoxide, sulfur dioxide, nitrogen oxides and hydrocarbons. Particles -
solid and liquid. These affect weather by: 1. collect water and help to form
clouds 2. some absorb or reflect insolation.
Air
Pressure - the weight of the overlying air. At the surface the pressure is
greatest; higher up, pressure decreases.
The atmosphere can be divided into layers according to composition,
function and temperature.
Composition
Profile: In terms of composition, the atmosphere is divided into the
heterosphere and homosphere. In the heterosphere (above 80 km), gases are
sorted into layers according to their atomic weight – the lightest gases, such
as hydrogen and helium, form the higher layers; heavier gases, such as oxygen
and nitrogen, form lower layers. Less than one thousandth of 1 percent of the
atmosphere’s mass is in the heterosphere. In the homosphere (below 80 km) gases
are almost* completely mixed together into what is commonly called “air” (*
exceptions are ozone and some variable gases). Much of the homosphere is made
up of uniform gases – meaning the proportion of these gases remains constant
from place to place and over time.
Function Profile:
In terms of function, the atmosphere is divided into two layers – the
ionosphere and the ozonosphere. Both layers function
to remove harmful radiation and charged particles from insolation. The
ionosphere, extending from 50 miles to 300 miles high, absorbs cosmic rays,
gamma rays, X-rays and shorter wavelengths of UV radiation. Atoms in the ionosphere are changed into
positively charged atoms or ions by
this absorption of energy – giving the ionosphere
its name. The ozonosphere is named after the ozone layer (12-31 miles high). The molecule ozone (O3)
is concentrated in this layer and absorbs UV radiation. The result of filtering
of insolation by the ionosphere and the ozonosphere is that it is mainly
visible light and infrared radiation that reaches the surface of the earth.
Temperature
Profile: The temperature profile of the atmosphere results from differences in
how different parts of the atmosphere absorb energy from the sun and earth.
Abrupt changes in temperature define four layers:
Troposphere - this is the lowest
layer where temperature decreases with height. On average the troposphere is
about 11 miles deep over the equator and 5 miles deep over the poles. This
layer is warmed by the earth's surface, which in turn is warmed by absorption
of visible light and infrared radiation from the sun. The farther from the
surface, the colder the air becomes. The top of the troposphere is the
tropopause, where temperature no longer decreases with height. Virtually all
WEATHER occurs within the troposphere. Weather is defined as atmospheric conditions prevalent
in a given place at a given time. Weather is essentially a temporary
phenomenon, changing from day to day or even from hour to hour.
Stratosphere – this layer lies
between approximately 11 and 31 miles high and is generally a zone of
increasing temperature: the maximum temperature of about 0o C is
reached at 31 miles, after which temperature stops increasing with height -
this marks the upper boundary to the stratosphere - the stratopause. The
stratosphere is heated by the absorption of UV radiation by the ozone layer it
contains.
Mesosphere – this layer extends
up to about 50 miles and is simply the layer of the atmosphere that becomes
colder with increasing distance from the heated stratosphere. The top of the
mesosphere, where temperature again begins to increase, is the mesopause.
Thermosphere - temperatures again rise in the thermosphere due to
the absorption of insolation by atmospheric gases. Temperatures can reach 2200oF
however, the air is extremely rarified (low density), so the actual amount of
heat present is low, despite the high temperatures.
The
troposphere is by far the most important layer because:
1. it contains about 75% of the mass of the atmosphere.
2. almost all atmospheric water vapor and particles are contained
within the troposphere.
3. almost all weather and climate takes place in the troposphere.
4. the tropopause acts as a "lid" on the troposphere, because it is a
temperature inversion (meaning temperature increases with height, which tends
to stop air from rising).
Solar
Energy and Temperature
Virtually
all energy received at the surface of the Earth is insolation. This energy is
in the form of electromagnetic radiation, which travels as waves and can be
classified by wavelength e.g. visible light = 0.4 - 0.7 micrometer wavelengths.
Both wavelength and intensity of radiation depend mainly on temperature - the
higher the temperature the shorter the wavelengths emitted and the higher the
intensity of radiation. E.g. Sun @ 60000 C emits short wave
radiation at a high intensity; Earth @ 150 C emits long wave
radiation at a much lower intensity. The output of insolation is constant = THE
SOLAR CONSTANT (2 calories per square centimeter per minute, or 2 Langleys per
minute).
Transmission:
The atmosphere transmits most of the Sun's short wave radiation (except UV
which is absorbed by ozone). However, long wave radiation given off by the
Earth is not readily transmitted through the atmosphere; for example, it is
absorbed by carbon dioxide - most is absorbed or reflected back to Earth -
especially if the sky is cloudy or contains particles. This "traps"
heat energy down near the surface and is referred to as the "Greenhouse
Effect" (i.e. radiant energy can get in but can't easily get out).
Scattering:
Some radiation is scattered as it passes through the atmosphere; short waves
are more effectively scattered than long waves, so the sky appears blue. At
sunrise and sunset the sky appears red because blue wavelengths are scattered
out during the longer passage through the atmosphere.
Absorption
and Reflection: Most radiation striking an object is either absorbed or
reflected. Absorption raises the temperature of the object (e.g. ozone, the
ground); reflection simply redirects the radiation without changing it. The
percentage of insolation reflected is known as the ALBEDO.
Transfer
of Heat to the Atmosphere: Absorption of radiation heats the earth's surface;
this heat is then transferred to the atmosphere by 1. Re-radiation - the
surface emits long wave radiation which is mostly absorbed by the atmosphere,
particularly if cloudy. 2. Conduction - transfer of heat by physical contact;
only heats a thin layer of air in touch with the surface. 3. Advection and
Convection - horizontal and vertical mixing of air transfers surface heat to
higher in the atmosphere.
Adiabatic
Heating And Cooling: As air rises it encounters lower pressure, expands and
cools; descending air encounters higher pressure, is compressed and become
warmer. Note: ADIABATIC means without energy loss or gain - the temperature
changes are caused by expansion or compression, not by input or output of
energy.
Overall,
for the whole planet on average, there is a balance between incoming and
outgoing radiation (if this were not true, the earth would grow progressively
hotter or colder); however, there are clearly differences in the amount of heat
received at different locations and in different seasons. What causes these
differences?
LATITUDE
is the major control on: 1. Angle of insolation 2. Length of day 3. Atmospheric
Obstruction - the length of travel by insolation through the atmosphere is
longer at higher latitudes; therefore there tends to be more absorption,
reflection and scattering, so less reaches the surface. These factors all
result in higher insolation at lower latitudes. The location of maximum
insolation coincides with the movement of the Sun - it is centered around the
Tropic of Capricorn in December and around the Tropic of Cancer in June.
However, this pattern is not perfect - locations at the same latitude do not
receive exactly the same heating - Why?
1.
CLOUDINESS - some place are more cloudy than others at the same latitude. 2.
LAND-WATER CONTRASTS - land heats and cools faster and to a greater degree than
water - why? i) water has higher specific heat (5X) ii) insolation penetrates
water (less concentrated) iii) water mixes (convection) iv) water evaporates -
this process uses heat energy -> less energy available to cause heating. The
result is that oceans MODERATE the temperatures of coastal regions - keeps them
cool in summer, warm in winter. The hottest and coldest temperatures occur in
the interior of large land masses, far removed from the oceans.
Latitudinal
Radiation Balance: there is a surplus of radiation in equatorial regions and a
deficit of radiation at high latitudes. In other words, between 280
N and 330 S there is more incoming short wave radiation than
outgoing long wave radiation, and this is reversed poleward of this region. Why
doesn't the surplus region get hotter and hotter and the deficit region get
colder and colder?
Answer
= The imbalance drives global atmospheric and oceanic circulations. These
movements of air and water carry surplus energy away from the tropics and
deliver it to the polar regions, thereby balancing the energy budgets. The
atmosphere is most important, accounting for 75-80% of this heat transfer.
Example
Questions
1.
The circumference of the Earth is about:
a. 10 000 km b. 25 000 km c. 40 000 km d. 55 000 km
2.
At the equator, 1 degree of longitude is about:
a. 2 km b. 11 km c. 55.8 km d. 111 km
3.
On which date are the noon sun's rays perpendicular to the surface at the
Tropic of Capricorn:
a. December 21st b. September 22nd c. March 20th d. June 21st
4.
The 3rd most abundant gas in the atmosphere is:
a. oxygen b. nitrogen c. carbon dioxide d. argon
5.
The angle of the noon sun's rays at the equator on September 22nd is:
a. 23.5 degrees b. 66.5 degrees c. 90 degrees d. 0 degrees