Chapter 1: Introduction to Earth Science

Section 2: A View of EarthSection 3: Representing

Earth’s Surface

Section 2: A View of Earth• Key Concepts

– 4 major spheres into which Earth is divided

– 3 main parts of the solid Earth– Theory of plate tectonics

Earth’s Major Spheres

• 4 major spheres:–Hydrosphere–Atmosphere–Geosphere–Biosphere

Hydrosphere• All water on Earth• Oceans: ~97%• Fresh water (lakes, streams, groundwater, glaciers): ~3%

Atmosphere• Reaches beyond 100 km above Earth

– 90% occurs within 16 km of Earth’s surface

• Provides protection from Sun’s heat & radiation

• No atmosphere life would not exist– No erosion/weathering surface

resemble moon

Geosphere• Beneath atmosphere & ocean• Not uniform

– 3 main parts (composition):• Core: dense • Mantle: less dense than core• Crust: lightest & thin; oceanic/thinner,

continental/thicker

Biosphere• Includes all life on Earth• Ocean floor up into atmosphere• Without life, the makeup & nature of

the other spheres of Earth would be very different.

Biosphere building at U of Arizona

Plate Tectonics• 2 types of forces affecting Earth’s

surface:1. Destructive forces: weathering,

erosion2. Constructive forces: mountain

building, volcanism• Theory of plate tectonics emerged

early 20th century – More than 50 years later

hypothesis theory– Explained how EQ and volcanic

eruptions occur and how continents move.

• Plates motion driven by unequal distribution of heat

Section 3: Representing Earth’s Surface

• Key Concepts– Lines on the globe & location– Mapmaker challenges– Topographic maps vs. other maps

To locate places N or S on Earth, cartographers use…

• Latitude: distance in degrees North/South of Equator; lines that run parallel to Equator

• Equator: 0°runs horizontally equidistance from the poles– points North of

equator= degrees N– points South =degrees

S

To locate places E or W on Earth, cartographers use…

• Longitude: distance in degrees E or W of the prime meridian– halves of giant circles running thru

Earth– Long. lines aka meridians

• Prime meridian: 0° long. – runs through Greenwich, England--

Royal Naval Observatory– Points west of PM designated W– Points east of PM designated E

• International Date Line: 180° long

• Note convergence of longitude lines as you approach the Poles…1° long=111km at the equator and 0 km at the poles

Degrees, minutes, seconds–To precisely describe the latitude of a place degrees, minutes and seconds are used. It looks like: ##°##’##”

– Why it matters? See below!

•1º lat=111 km on Earth’s surface =(40,000 km circumf./360°)

•1’ lat=1.85 km on Earth’s surface =(111 km/60’)

• 1” lat=.03 km on Earth’s surface =(1.85 km/60”)

Minutes and Seconds For precision purposes, degrees of longitude and latitude have been divided into minutes (') and seconds ("). There are 60 minutes in each degree. Each minute is divided into 60 seconds. Seconds can be further divided into tenths, hundredths, or even thousandths. 

Types of Maps

• Globes (not a map)• Projection Maps

– Mercator projection– Robinson projection– Conic Projection– Gnomonic

Projection

• Topographic Maps– Geologic Maps

• Legends & Scales

Globes

• Mapmakers wanted to present information accurately

– Mimics shape of Earth– Can’t be complete enough to be useful for

finding directions and can’t be small enough to be convenient for everyday use.

Projection Maps• Imagine a light inside a globe shining out. Wrap a

clear transparency around the globe. Trace the outline of the shadow of the land on the transparency.

• Takes the round globe & flatten it outPro: Easy to travel withCon: Creates a lot of distortion at poles

• Types: Types Visually

o Mercatoro Conico Robinsono GnomonicProportional?flattening the earthanimation flattened globe to map

Robinson

• Most widely used• Pro: Show most distances, sizes, and

shapes accurately• Con: distortion around edges of map

Mercator Projection• Sheet wrapped

around the globe• Creates parallel

lines of lat & longPro: straight lines

allow easier

navigation (planes/ships)Con: lots of distortion

of land shapes as

you reach higher latitudes

• Greenland appears as big as S. America but it’s really 1/8th the size of S. America!!

Conic Projection • Areas below red line would appear HUGE as areas near poles look smaller.

• Projecting points/lines from globe onto cone @ lines of latitude

• Pro: Little distortion of spots touching cone/ line of lat., used to map small areas (road/weather maps)• Con: Lots of distortion

near top and bottom of map

Gnomonic Projection• Points/lines from globe

projected on paper that touches globe at 1 point

• Pro: No distortion at contact point• Con: Lots of distortion in direction & distance between landmasses

• Note little distortion near Greenland & much in the S. US

• Great accuracy the shortest distance between two points—straight line great for

navigation!

Topographic Maps

• Bird’s eye view of an area

• Show Earth’s 3-D in 2-D

• Shows how steep/gentle a slope is

• Shows the elevation & shape of the land and other geographic or cultural (bridges, schools, churches, cemeteries, etc) features

Vocab: Topographic Maps• Contour lines:

connect points of equal elevation

• Contour interval: difference in elevation between adjacent contour lines

• Relief: difference in elevation between highest & lowest points on map

• Index contour: every 5th line on the map is bold and elevation is marked for reference

Contour line rules…

• Contour lines are continuous closed loops; they never just appear or end on a map except at the edges

• Separate higher elevations from lower elevations

• Never cross (run together=cliff)• Closer lines=steeper slope• Closed depressions are marked with hachures

(point in direction of drop)• Water flows perpendicular to contour lines

Geologic map

• Color coded to show rocks below the soil– Distribution– Arrangement– Type of

rock/minerals– Age of rock

• Often superimposed over topographic maps

All maps have…

Map Legends• Shows symbol images• Decodes their

meanings

Map Scales• Shows distances on a

map• Ratio between

distances on map and actual distances on Earth’s surface

Remote Sensing: gather data about Earth using instruments on satellites, planes or ships; more accurate

• Landsat satellites• Weather satellites• Navigation

satellites• Very Long Baseline

Interferometry (VLBI)

• Global Positioning System (GPS)

• Geographic Information System (GIS)

Landsat• Satellites detect

features based on the warmth (diff frequencies) they radiate

• Detectors on mirrors measure the intensity of energy received digital images

Weather Satellites

• Monitor atmospheric temperature, humidity, cloud cover, etc.

• Help locate sources of distress signals• Able to scan surface in one 24-hour

period

The first picture of Earth from a weather satellite, taken by the

TIROS-1 satellite on April 1, 1960. Although primitive in comparison with

the images we now receive from satellites, this first picture was a

major advance.

Navigation Satellites

• Assist ships and submarines to determine location

Very Long Baseline Interferometry (VLBI)• Utilizes large network of antennas globally

to receive radio waves from space objects (quasars)

– Using the arrival times of radio waves from quasars, the position of radio telescopes on Earth are determined to within millimeters of their position.– Able to study tectonic plate movement due to changes in telescope position

GPS[Global Positioning System]

• Satellite navigation system using microwaves– 27 satellites 12,000

miles from Earth– Constantly orbit– Orbit Earth twice/day– Accuracy 10 m

• Triangulate location based on signals received from 3 sats.

• Signal from 4 sats. would allow for elevation calculations

• GPS tutorial

Importance of Triangulation

•Able to pinpoint given location

•Minimum of 3 satellites needed to triangulatewhere all 3 circles intersect is where your given location is!

GISGeographic Information System

[computer based program]

• Combines map types we’ve discussed – Layers info one on top of another

• Topography of land• Elevation• Roads, buildings, etc

– Monitor changes to a specific area over time

• Volcanic eruptions• Flooding of an area• Animal population trends• Define vector/raster!