Physical Geography exam 1

What is geography?

• Geography- the study of the spatial relationships among Earth’s physical and cultural features and how they change over time

• 3 branches of geography- Physical geography, Human geography, and Geographic Techniques 

Physical Geography

• studying Earth’s living & nonliving physical systems (oceans, rivers, climate, the biosphere) How the systems change through space and time naturally or by human activity 

• What is a system?

  • Set of interacting parts/processes that function as a unit

  • This class (learning system)

  • Or a tree (ecosystem)

  • Or anything & everything

  • Open vs. Closed (near impossible)

  • Almost all systems are open system 

  • Can be altered by human activities and natural processes 

• What other impacts do human activities have on the natural environment?

  • Deforestation, climate change, mining, dams, introducing invasive species, levees, pollution, wildfires

• Scales

  • Spatial- the physical size, length, distance, or area of an object, or the physical space occupied by a process

  • Temporal- the window of time used to examine phenomena and the process or the length of time over which they develop or change; different physical phenomena or processes occur on different temporal scales from minutes, to years, to millions of years 

The physical Earth

• Matter and energy

  • Matter- Any material that occupies space and has mass (states of matter) 

  • Energy- performs work on or can change the state of matter

• Types of energy

  • Radiant- the sun (most important)

  • Kinetic energy- energy of movement

  • Potential energy- stored in an object

  • Geothermal- heat from Earth’s interior

  • Chemical- released through chemical reaction 

• Earth’s physical systems

  • Atmosphere- the layer of gases surrounding Earth

  • Biosphere- all life on Earth

  • Lithosphere- the rigid outer layer of Earth, called the crust, and the heated layer beneath it down to about 100 km (62 mi)

  • Hydrosphere- all of Earth’s water in its three phases solid, liquid, and gas

Atmospheric systems

• Weather- the state of atmosphere at any given moment

• Climate- the long-term average of weather and the average frequency of extreme weather events 

Earth’s shape

• Earth is an oblate spheroid (an imperfect sphere) due to:

  • Distortion from Earth’s rotation

  • Gravitational anomalies

  • Relief (variations in elevation) Highest point: mt everest Lowest point: dead sea

  • The equator has the fastest rotation speed

  • The higher latitude the slower rotation speed 

Mapping earth

• The geographic grid, latitude & longitude 

• Latitude

  • North and south of the equator

  • Equator (0), Poles (90 N, 90 S)

  • Also called parallels 

  • Latitudinal zones 

• Longitude

  • East and West of the Prime meridian

  • Prime meridian (0)

  • International date line (180)

  • Also called meridians

  • Globally three are 360 meridians 

• At 0 latitude, the distance between two nearby meridians (say 0 and 1 E) = 111km or    69 mi

• At 60 N, the distance between two nearby meridians (say 0 and 1 E) = 56 km or 35mi

• At the equator (0) what's the distance between 50 E and 80 E? 3,300 km or 2070 mi

• At 60 N what's the distance between the two same meridians? 1680 km or 1050 m

Using the grid

• Latitude and longitude are given in degrees, minutes, & seconds

• Northern and Eastern hemispheres are given in positive numbers

• Southern and Western hemispheres are given in negative numbers

Maps 

• Maps are the most efficient means of communicating spatial information

• All maps reduce the size of geographic 

• Putting Earth’s curved surface onto a flat map creates distortion

• Different map projections correct for distortion 

Map scale

• Specifies how much the real world has been reduced

  • Bar scale (graphic map scale)

  • Verbal scale (e.g, 1 cm = 1 km)

  • Representative Fraction Scale (e.g, 1/100,000)

  • Maps also should have other elements for effectiveness and reliability (e.g, title, legend, direction arrow, date)

Contour lines

• Lines of equal elevation in relation to sea level used on topographic map

  • Always connect back to themselves, forming a closed loop

  • Never cross each other

  • Only converge on vertical cliffs 

Imaging Earth

• Remote sensing-

  • collect physical info without direct contact with the subject 

  • Doppler radar (Radio Detection and Ranging)

  • Sonar (Sound Navigation And Ranging)

  • LIDAR (Light Detection and Ranging)

  • Radar and LIDAR can be used to make Digital Elevation Model (DEM)

  • DEM- a digital representation of land surface or underwater topography

• Geographic Information systems (GIS)

  • Uses computers to capture, store, analyze, and display spatial data

  • Advantages: Interactive, continually refined, each layer serves a purpose

Portrait of the Atmosphere 

Why should we care about air?

• We breathe it

• Air pollution threatens human health (Ex: burning of fossil fuels or volcanic eruptions)

• Composition of the atmosphere: Nitrogen 78%, Oxygen 20%, Argon 1%, Carbon dioxide 0.09%

Two major groups of gases

• Permanent gases: amounts fluctuate only a little

  • Just over 99% of Earth’s atmosphere is composed of two permanent gases Nitrogen & Oxygen

  • Major gases:Nitrogen, Oxygen,& Argon

• Variable gases(trace gases): exists in extremely small quantities and change in their amounts

  • Greenhouses gases are one category of variable gases (H20, CO2, & O3)

• Major gases- Nitrogen (N) 78%

  • N2 gas- diatomic N

  • Relatively inert

  • We do not us the N2 we breathe

  • Key to life- food, DNA

• Major gases- Oxygen (O) 21%

  • O2 gas - diatomic O

  • Highly reactive

  • By product of photosynthesis

  • Essential to life 

• Major gases- Argon (Ar) 0.93%

  • Argon gas

  • From radioactive decay and formation of Earth

  • Inert gas 

  • Industrial uses 

• Variable gases- water (H20) 0-4%

  • Variable in atmosphere

  • Essential to life

  • Hydrological cycle

  • Exists as vapor, liquid, and solid in atmosphere

  • Spatially variable 

  • Which latitude has the most water vapor? 0 degrees 

• Variable gases- carbon dioxide (CO2)

  • From respiration

  • Greenhouse gas

• In warmer seasons the rate of photosynthesis increases which means more CO2 increases

Gas sources and sinks

• Gases enter the atmosphere through a source and leave through a sink

• Oxygen

  • Source: Photosynthesis

  • Sink: decomposition and weathering of rockers absorb O2 from the atmosphere

• Water vapor

  • Source: evaporation from oceans, plant photosynthesis, and volcanic eruptions

  • Sink:Condensation and decomposition convert H2O to liquid and solid (ice) states

• Carbon dioxide 

  • Source: volcanic eruptions, decay of living matter, respiration, humans’ burning or coal, oil ,& natural gas for energy

  • Sink: plants, oceans, and chemical reactions with rocks absorb CO2

 More details- the troposphere

• As one moves higher in the troposphere, air temperature generally decreases

• The weather layer 

• Roughly 80% of the atmosphere’s mass is in the troposphere

• Where all Earth’s weather occurs

• Experiences strong vertical mixing

• Almost all clouds, and all storms and precipitation, are limited to the troposphere 

• The top of the troposphere is called the tropopause

  • Almost all cloud tops end at the troposphere,  due to the temperature inversion in the stratosphere 

• Height of the tropopause: average height is about 12 km (7.5 mi)roughy twice as high over the equator as over the poles

• German shepherd 

Stratosphere: a protective shield

• Contains permanent temperature inversion (air temp goes up with increased height) 

• Cause of temperature inversion: absorption of ultraviolet (UV) radiation by stratospheric ozone

• Ultraviolet (UV) radiation-solar radiation that represents the light that has shorter wavelengths than visible light

• Ozonosphere-a region of the stratosphere with high concentrations of ozone molecules that block UV radiation

• Very few clouds and no storms, mostly free of atmospheric aerosols, air flows horizontally, & permanent temperature inversion 

• Bulldog 

Mesosphere and the thermosphere

• Meteors vaporize in the mesosphere

• Auroras occur in the thermosphere (permanent temperature inversion)

Ionosphere

• A region of the upper mesosphere and the thermosphere where nitrogen and oxygen are ionized by solar energy 

Auroras

• Aurora Borealis (northern lights and Aurora Australis (southern lights) occur in the ionosphere

• Cause? Gas molecules energized by charged particles called solar wind

• Where? Found mostly near the poles where Earth’s magnetic field concentrates solar wind’s particles 

The exosphere

• The region where molecules are free of Earth’s gravity 

Primary and secondary pollutants

• Primary- enters the air or water directly from natural or anthropogenic sources (CO2, CO, & SO2)

• Secondary- forms in the air or water through chemical reactions among primary pollutants 

Primary pollutants

• Carbon monoxide (CO)

  • Natural sources of CO include volcanic eruption, forest fires, bacterial princesses, and natural chemical reactions in the troposphere

  • Vehicles are the largest anthropogenic source of CO due to the incomplete combustion 

• Sulfur dioxide (SO2)

  • Emitted from natural and anthropogenic sources (volcanic eruptions and burning fossil fuels

  • Over 80% of anthropogenic SO2 emissions originate from burning coal to generate electricity 

• Nitrogen Dioxide (NO2)

  • A toxic reddish- brown gas produced mainly by vehicle tailpipe emissions

  • Irritates lung tissue and, with chronic exposure can lead to serious respiratory problems

  • Also caused by burning coal emissions 

Temperature inversions in the troposphere

• Often develops in valleys  

• Usually no more than a few hundred meters thick

• Can trap pollutants near the ground surface

The clear air act of 1970

• Imposed strict regulations on emissions of air pollutants

• Has been effective at reducing air pollution, saving lives, and reducing health care-related costs 

Chlorofluorocarbons (CFCs)

• Synthetic ozone- degrading compounds used mainly as refrigerants, aerosol propellants, and fire retardants 

• CFCs have accumulated in the atmosphere

• CFCs linger in troposphere for decades and destroys ozone in the ozonosphere

• Montreal protocol- an international agreement banning further production of CFCs

• HFCs replace CFCs

 Solar energy and seasons 

People and the seasons

• All locations on earth experience seasons 

• Some locations have more meteorological seasonality (temp variations) than others 

• Many human activities and holidays mark seasonal events 

What is temperature

• Temperature- average kinetic movement of atoms and molecules of a substance

• Molecules move quickly in objects with temps and relatively slowly in objects with low temps 

• Thermal expansion: matter expands when heated and contracts when cooled 

• When molecules are no longer moving a point of 0 K(-273.15 C) or absolute zero is reached

Temperature scales

• One unit increase in the celsius scale is the same as 1.8 degree increase in the fahrenheit scale 1 C -> 1.8 F

• The formula for converting celsius:  F=(1.8 x C) + 32

• What’s water’s freezing temp? 0 C= 32 F 

• The formula for converting Fahrenheit: C= (F-32)/1.8

• What's water's boiling temp? 212 F = 100 C 

• One unit increase in the kelvin scale is the same as a one-degree increase in the celsius scale (1K = 1C)

• The formula for converting C to K: K=C +273.15

• The formula for converting K to C: C=K- 273.15

Heat

• The internal energy transferred between materials or systems due to their temperature differences

• The kinetic energy of molecular movement can be felt as heat 

Four ways heat moves

• Conduction, convection, advection, & radiation 

• Conduction

  • Process by which energy is transferred through a substance or between objects in direct contact (touching)

• Convection

  • The transfer of heat through vertical movement of mass within a fluid (liquid or gas) 

• Advection

  • The horizontal movement of some property of atmosphere (heat, humidity, or pollutants) 

• Radiation

  • Process by which wave energy travels through the vacuum of space or through a physical medium such as air or water 

Radiant energy

• Energy that is propagated in the form of electromagnetic waves

• All forms of radiation have both electric and magnetic properties referred to as electromagnetic energy 

• How fast do electromagnetic waves travel? Light speed (300,000 km per sec) 

Photons and wavelengths

• All matter emits photons (packets of energy) of electromagnetic radiation 

• Photons travel in waves. The distance between the peaks of two waves is the wavelength 

• The electromagnetic spectrum (EMS)- the full range of wavelength of radiant energy

• The hotter something is, the shorter its wavelengths are 

• Wien’s law- wavelengths are inversely proportional to temps

• Describes the relationship between the temp of a blackbody(an ideal substance that emits and absorbs al frequencies of light) and the wavelength at which it emits the most light

Shortwave and longwave radiation

• Objects with higher temps emit photons at a higher frequency (# of waves) & shorter wavelengths than objects with lower temps 

• Sun: high temp, high frequency, shorter wavelength

• Earth: low temp, low frequency, longer wavelength 

• Most solar radiation is shortwave radiation (SWR)

• All radiation emitted by Earth's longwave radiation (LWR)

Earth’s important wavelengths: ultraviolet, visible, and infrared

• 99% of the sun's energy emission are in the three wavelength categories

• Ultraviolet (UV) radiation

  • Accounts for ~10% of the sun’s energy output

  • Most of them are absorbed by ozone in the stratosphere

  • Clouds and aerosols help determine how much UV radiation reaches Earth 

• Visible radiation (light)

  • Accounts for 44% of solar radiation

  • When all visible light colors are combined they blend into white 

  • Black (true darkness) is the absence of all light 

  • Rainbows are the result of refraction process that breaks up visible light into seven colors inside water droplet 

• Infrared radiation (IR)

  • IR has wavelengths longer than visible radiation 

  • Earth absorbs shorter solar radiation and re-emits it as infrared (longwave) radiation 

Insolation

• Incoming solar radiation 

• As insolation travels through the atmosphere, it is transmitted, scattered, reflected, and absorbed by the air, rocks, plants , and water 

• Transmission

  • The unimpeded movement of electromagnetic energy through a medium such as air, water, or glass

  • The atmosphere absorbs UV and IR wavelengths but transmits visible wavelengths

  • Glass transmits visible light but absorbs UV wavelengths 

• Scattering

  • The process of redirecting solar radiation in random direction as it strike physical matter 

  • Sky colors due to scattering, shorter wavelength of light (like blue) scatter easier than longer wavelengths ( like red and orange) 

• Absorption

  • The ability of an object or material to assimilate electromagnetic energy and convert it to another form of energy 

• Reflection

  • The process of returning a portion of the radiation striking a surface in the general direction from which it came

  • Lighter-colored surfaces have a higher reflection (less absorption) than darker surfaces 

Albedos

• Albedo- reflectivity of a surface given as the % of incoming radiation that it reflects

• A perfect mirror has an albedo of 100% 

• The albedo of Earth, taken as a whole, is 31%

• Earth’s surface albedo varies from region to region

• Surfaces with low albedo absorb more insolation than do objects with higher albedo 

• Earth does not emit visible light but only reflects it

• Earth is visible from space bc it reflects sunlight 

Causes of the urban heat island

• An urbanized region may become warmer than surrounding rural areas 

  • Cities have low albedos

  • City materials retain absorbed heat energy and radiate it 

  • Cities lack water for evaporation (cooling) 

The great balancing act

• Temp of Earth’s surface and atmosphere is the result of a balance between incoming and outgoing energy 

• Radiative equilibrium temperature- temp of an object resulting from the balance between incoming and outgoing energy (Earth:15 C)

The greenhouse effect

• The process by which the atmosphere is warmed as greenhouse gases & clouds absorb and counter-radiate heat 

• Without any greenhouse gases, Earth’s lower atmosphere would be much colder (-18 C, inhospitable to most life)

• Humans have modified the greenhouse effect by adding greenhouse gases to the atmosphere 

The global heat engine

• At most latitudes, there is either a surplus or a deficit of heat. But where?

• Heat from tropics is advected (horizontal movement of energy) poleward by the atmosphere (AKA the winds) and oceans (AKA ocean currents) 

• The movement of heat from low to high latitudes (and altitudes) as a result of heating differences

• Almost all atmospheric movement (wind, tornados, ect) is the result of heating inequalities across latitude and altitude 

The four seasons 

Orbit

• Flat plane of the orbit-> plane of the ecliptic

• Earth is closer to the sun in january (perihelion) than it is in July (aphelion)

• January receives 7% more energy 

What causes seasons

• Seasons are NOT caused by the changing distance between Earth and the sun 

• Seasons are caused by the tilt of Earth’s axis (23.5 degrees) 

The movement of Earth

• The earth is rotating on its axis

• The Earth orbits around the sun every 365.25 days (.25 causes leap year every 4 yrs)

The subsolar point

• Single point at which sun’s rays are perpendicular to Earth’s surface at or near noon

• Latitude of the subsolar point (solar declination) is always 90 degrees away from the line separating night from day (circle of illumination)

• Subsolar point determines angle of the sun above the horizon (solar altitude) and thus intensity of noontime Sun  

Migration of the subsolar point

• Subsolar point migrates between the Tropics of Cancer (23.5 N) and Capricorn (23.5 S) 

• March and september equinoxes: subsolar point crosses equator (every place on earth has 12 hrs of daylight and 12 hrs of night)

• December solstice: subsolar point is at the Tropic of Capricorn (antarctic circle experiences 24 hrs of daytime)

• June solstice: subsolar point is at the Tropic of Cancer (arctic circle experiences 24 hrs of daytime) 

Solstices, equinoxes,and day lengths

• Equinoxes (0)- all locations on Earth have 12 hrs of day & night

• June solstice- longest day of the year in the northern hemisphere. Days get shorter after the June solstice until we reach the…

• December solstice- shortest day of the year in the northern hemisphere. Days get longer after this until june solstice

• Everything is opposite in the southern hemisphere 

Tilt and seasonality

• If Earth’s axis had no tilt; subsolar point would always be on the equator; no seasonal change 

Temperature patterns & seasonality 

Surface temp patterns

• Elevation

  • In the troposphere temp decreases with altitude

  • Mountains are always cooler than surrounding lowland regions 

• Latitude

  • Temp generally decreases away from the equator as sunlight becomes more diffuse 

  • Lower surface temps & greater annual range at higher latitudes 

• Annual temperature range (or seasonality): difference between the avg max and avg min

What controls seasonality patterns?

• Latitude- high latitude have a greater annual temp range than low latitudes

• Proximity to the oceans: continental (inland) locations have a greater annual temp range than maritime(coastal locations) 

• Other factors: Ocean currents, prevailing wind, etc. 

Why do inland regions have greater seasonality than coastal regions?

• Specific heat of water

  • Heat capacity: the amount of heat that must be absorbed to change  the temp of an object

  • Specific heat capacity- the heat capacity of 1 gram of an object

  • Contents are generally warmer in the summer than oceans (maritime effect) 

  • In winter continents are colder than oceans (continental effect)

  • Isotherm: a line on a map connecting points having the same temp at a given time 

• Evaporation of water

  • Evaporation cools water and prevents it from becoming warmer… land heats up more in sunlight than oceans do 

• Water transparency

  • Since water is transparent and land is opaque convection mixes water warmed by sunlight with cooler water at great depths

• Water mixing

  • Land surfaces heat up faster and to a higher temp than water

• Ocean currents

  • Ocean-atmosphere heat transfer- warm ocean currents (gulf stream) raise avg annual temp and reduce annual temp range 

• Prevailing winds

  • Wind is from the west so west coasts generally have maritime climates and east coasts have continental climates