Regents Earth Science – Unit 3: Measuring EarthModels

Model - a representation of an object or natural event

• maps

• globes

• drawings

• diagrams

• graphs

• formulas

Earth's Shape

Oblate Spheroid - true shape of the Earth

• slightly flattened at poles, bulging at the equator

• from space it looks like a perfect sphere

• equatorial diameter = 12,756 km.

• polar diameter = 12,714 km.

Gravity - pulls inward equally in all directions

• causes the Earth to be spherical

• Earth's rotation on its axis causes the Earth to bulge

at the equator

Evidence of Earth's Shape

1. Photos from Space - reveal Earth is spherical

2. Observations of ships on the horizon - appearance and/or disappearance of ships

Evidence of Earth's Shape3. Observations of lunar eclipses - show Earth is

spherical

4. Measurements of gravity - pull of gravity is stronger the closer you are to the center of earth

– force pulling down at poles is greater than at the equator (closer to the center of the Earth)

5. Observations of the North Star (Polaris) - altitude of Polaris changes as an observer moves

north or south (in Northern Hemisphere)

Latitude and Longitude

Latitude - angular distance north or south of the equator (0°)

• run east-west

• measure north-south

Parallels - east-west circles on maps and globes

• equal distance from each other (parallel)

• look like lines from equatorial view

latitude - like rungs of a ladder

Latitude and Longitude

Longitude - angular distance east or west of the Prime Meridian (0°)

• maximum longitude = 180° (International Date Line)

Meridians - north-south semicircles on maps and globes that connect the north and south poles

• any location above the Equator has a latitude of north

• any location below the Equator has a latitude of south

north

south

• any location to the right of the Prime Meridian has a longitude of east

• any location to the left of the Prime Meridian has a longitude of west

westeast

Equatorial view:

latitude longitude

Polar view:

Equator (0° latitude)

Prime Meridian (0° longitude)International Date Line

(180° longitude)

Latitude and Longitude

Time ZonesEvery 15° of longitude equals 1 hour of time

• when moving east (to the right) time is later

• when moving west (to the left) time is earlier

6 a.m.6 a.m.6 a.m.

7 a.m.7 a.m.7 a.m.

8 a.m.8 a.m.8 a.m.

9 a.m.9 a.m.9 a.m.10 a.m.10 a.m.10 a.m.

• Earth takes 24 hours to rotate once on its axis

sunlightsunlight

6 am4 am

2 am

12

midnight

10 pm

8 pm6 pm

4 pm

2 pm

12 noon

10 am

8 am

360°

24 hrs.=

15°

1 hr.

*** Earth rotates 15°/hour

Reference Tables p.4

Time ZonesEarth has 24 time zones:

Earth FieldsField - any region of space that has some measurable value of a given quantity at every point

• temperature

• air pressure

• elevation

isoline - a line that connects points of equal value

1. isotherm - connects points of equal temperature

2. isobar - connects points of equal air pressure

3. contour line - connects points of equal elevation

Isolines:

• never cross

• can run-off map

• never end

isotherms - temperature

field map of the U.S.

topographic maps show the elevation of the land by using contour lines

Topographic Maps

• man-made features are shown by using symbols

Topographic Maps

elevation - height above sea level

contour interval - difference between 2 adjacent

contour lines

benchmarks - show the exact elevation

contour interval = 25 m

x highest possible elevation at x = 174m

index contour line - every 5th line is darkened and labeled

• helps to read maps

depression contour line - special

contour lines that have hachure

marks on the inside

x

depression contour

line elevation =

240m

• used to show a depression (ex.

crater) on Earth's surface

minimum elevation at x = 221m

contour lines always bend upstream

• lines "point" to higher elevation

• streams flow from high to low elevation

(flow opposite the direction the contour

lines point)

stream flow

contours make a "V" that

points upstream

high elevation

Topographic Maps

• Gradient - the rate at which field values change

from point to point in a field

B

200m - 100m

2 km.

50.0 m/km.

A

G =∆FV

d

G =

G =

G =∆FV

d

Reference Tables p.1

• the gradient is steepest where the contour lines are closest together

• the gradient is gentle where the contour lines are far apart

Profile - exaggerated side view of a portion of the earth's

surface along a line between two points

Topographic Maps

1. draw a line between 2 points on a map

2. place a blank piece of paper along the line you

have drawn

3. on the blank paper, make a tic mark wherever the

paper crosses a contour line on the map and label

the elevation for each mark

4. on graph paper, make an appropriate vertical scale for elevation

5. place the paper with tick marks along the horizontal axis of the graph

and go directly above the tic marks on your paper and make a small dot

on the graph paper at the corresponding elevation

6. connect the data points

Spheres of the Earth

1. Atmosphere - shell of gas that surrounds the Earth (least dense)

2. Hydrosphere - the waters of the Earth (oceans, lakes, rivers, groundwater, ice)

3. Lithosphere – crust of the earth, dense outer shell composed of rock (most dense)

AtmosphereThe Earth's atmosphere has several distinct layers

• Troposphere – lowest layer, temperature decreases with increasing altitude, has “weather” due to the presence of water vapor

• Stratosphere – above the troposphere, temperature increases with increasing altitude, contains the ozone layer

• Mesosphere – above the stratosphere, temperature decreases with increasing altitude

• Thermosphere – outermost layer, extends into space, temperatures increase with increasing altitude

• the interface between each layer occurs where temperature trend changes

• the boundary between each layer is a pause:

Reference Tables p. 14

• pressure decreases with increasing altitude

Reference Tables p. 11

Hydrosphere

Almost ¾ (71%) of the Earth’s surface is covered in water

• very thin layer only 3-4 km. thick (like the skin of an apple)

• includes oceans rivers, and lakes

Earth’s InteriorEarth’s interior has 5 zones:

1. Lithosphere – rigid, broken into several plates

2. Asthenosphere – “plastic like” layer, lithospheric plates are moved by convection currents

within this zone

3. Mantle – stiffer than asthenosphere, but heat is transferred by convection

4. Outer Core – liquid, made of nickel and iron

5. Inner Core – solid, made of nickel and iron

• temperature, density, and pressure increase with depth

• outer core is liquid (actual temperature is greater than the melting point)

Reference Tables p. 10