Topic 2Origins--The Universe,

Solar System, Earth

GEOL 2503Introduction to Oceanography

Important Ages

• Universe—about 15 billion years old

• Solar System—about 5 billion years old

• Earth—about 4.6 billion years old

A supernova exploded 5 billion years ago. A shock wave sent a nearby nebula into a spin. The Nebula, a cloud of gas and dust, contracted and heated, forming the Sun. Outer dust particles collided, clumped together, and formed the planets

Early Planet Earth

• Bombarded by particles of all sizes• Material accumulated• Interior temperature increased• Very hot, homogenous composition• Layers formed by differentiation--lightest

material to the surface, heaviest material to the center

Differentiation give us a layered planetEarly Earth heats up due to radioactive decay, asteroid impacts. Denser material sinks, lighter material rises.

http://www.indiana.edu/~geol105/images/gaia_chapter_3/

earth_differentiation.htm

Earth—A differentiated planet

• Atmosphere, density less than 1g/cm3

• Hydrosphere, 1g/cm3

• Crust, 2.7-2.9 g/cm3

• Mantle, 3.3-5.6 g/cm3

• Core, 10-14 g/cm3

Density

• Mass per unit volume• D = M/V• grams per cubic centimeter (g/cm3)• kilograms per cubic meter (kg/m3)• pounds per cubic foot (lb/ft3)

Mantle—the layer between the core and the crust

Core—the center of the Earth is molten on the outside and solid on the inside We’ll see more in plate tectonics

How did the oceans form?

• Water vapor came to the surface during heating of the interior

• The vapor condensed at the cooler surface to form the oceans

• Perhaps most important was water brought to Earth as ice in comets

Natural Time Periods• Year• Month• Day• Seasons

• Many oceanographic and biologic processes are controlled by these time periods

Year

• Time it takes for Earth to complete one orbit around the Sun

• 365 ¼ days• Adapted to 365 days for convenience• Add an extra day every 4 years—leap year

Earth’s Orbit

Earth’s orbit is an ellipse, not a circle. Average distance to Sun is 93 million miles (1 Astronomical Unit).

SUN

What causes the seasons?

The 23 ½° tilt of Earth on its axis

First day of summer (summer solstice)—June 22—Sun is directly above the Tropic of Cancer (23.5 degrees north)First day of autumn (autumnal equinox)—September 23—Sun is directly above the equatorFirst day of winter (winter solstice)—December 21—Sun is directly above the Tropic of Capricorn (23.5 degrees south)First day of spring (vernal equinox)—March 21—Sun is directly above the equator

Important Seasonal Dates (see previous slide)

Lunar Month

• The time for the moon to pass through all 4 phases:– new moon, first quarter, full moon, last quarter

• 29 ½ days• 4 phases approximately match the 4 weeks

of the month

Solar Day• Time for the

Earth to make 1 rotation on its axis

• 24 hours

The Shape of the Earth• Nearly spherical • Slight bulge at the

equator• Mount Everest is the

highest mountain—29,000 ft

• Challenger Deep is the deepest ocean depth—36,000 ft

How do we locate ourselves on the planet?

Latitude & Longitude• Location system• Grid superimposed on the Earth’s surface• Use crossing of latitude and longitude lines to

identify locations• Each latitude/longitude intersection is unique

Latitude

-Measured north and south from the equator

-Lines of latitude are always parallel

-Circumference decreases to zero at poles

Latitude• Also called parallels• Begin at the equator—O° latitude• All lines of latitude are parallel (what is the

definition of parallel lines?)• North Pole—90° N• South Pole—90° S• Lines (circles) of latitude become smaller as the

poles are approached

Latitude (parallels) can be used for measurement—Why?

• 1 degree of latitude equals 60 nautical miles• Each degree divided into 60 minutes• 1 minute of latitude equals 1 nautical mile• Each minute divided into 60 seconds

• Why can’t longitude be used for measurement?

Longitude

-Measured east and west from the Prime Meridian

-All meridians are the same size

-Meridians converge at the poles

Longitude

• Also called meridians• Begins at the prime meridian—0° longitude• International date line—180° longitude• Lines run from North Pole to South Pole• Think of orange segments• Identified by degrees east and west of the

prime meridian

Great Circles• A great circle is created by a plane

crossing a sphere at its center

• A great circle divides the sphere in two equal hemispheres

• A small circle is created by a plane crossing a sphere not at its center

All lines of longitude are great circles.

The equator is the only line of latitude that is a great circle.

great circle

small circle

The prime meridian, set by international agreement, runs through the Old Royal Observatory in Greenwich, England

http://www.lat-long.com/

Degrees Minutes Seconds: Latitude: 33° 34′ 48″ NLongitude: 085° 04′ 36″ W

Decimal Degrees:Latitude: 33.58Longitude: -85.07667

Location of Carrollton, Georgia

Geographic Coordinates (Globe)(earth is divided into 360º)

Label on globe:EquatorPrime MeridianTropic of CancerTropic of CapricornArctic CircleAntarctic Circle30 N 30 S30 W60 W90W

Longitude and Time

Circle or sphere has 360 degrees

Earth rotates once in 24 hours

Thus, Earth turns 15 degrees per hour

Local “noon” is when the sun is directly overhead

Longitude and Time

• Earth turns 15 degrees per hour• With an accurate clock we can measure

Earth’s rotation• The prime meridian is zero longitude• The universal clock is set to noon when the

sun is directly above the prime meridian• Greenwich Mean Time, Universal Time,

Zulu Time

Longitude and Time

• Forget about time zones, think about universal time

• If it’s noon in Greenwich, England, what time is it in Carrollton?

• In other words, how many times zones are we from Greenwich, and in what direction?

• Five, to the west, our noon (EST) = 1700 GMT• Except during DST when our noon = 1600 GMT

Longitude and Time

• A position west of the prime meridian that is directly under the Sun at 1:00 P.M. GMT is 15° W.

• A position east of the prime meridian that is directly under the Sun at 11:00 A.M. GMT is 15° E.

John Harrison (1693-1776)

• British clockmaker• Solved the “longitude problem”• Built first chronometer in 1735• Fourth model (1761) lost only 51 seconds

on 81-day voyage• Captain Cook used Harrison’s chronometer

to help produce accurate charts

John Harrison’s fourth marine chronometer—portable and accurate enough for determining longitude.

Navigation

• Radar• Loran• Global Positioning System

Radar

• Radio detecting and ranging• Image is displayed on a radar screen when

radio pulses are sent out, reflected from an object, and returned to the antenna

Loran

• Long-range navigation• Measures the difference in arrival time of

radio signals from pairs of land stations

Global Positioning System

• GPS• Navigational satellites transmit digital codes

through radio signals to ground receivers• Receivers generate identical codes at the

same time

One of the GPS system’s NAVSTAR satellites

Types of Maps

• Contour map—areas of equal value• Topographic map—elevation on land• Bathymetric map—water depth• Physiographic map—uses color and

shading to show perspective• Nautical charts—details for navigation,

especially nearshore hazards

Contour Map Contours connect points of equal value

Figure 02_12

Figure 02_13

Topographic Map

• Using shading and detailed labeling, topographic maps show a lot of detail of land cover

Topographic Maps• Topographic maps use contour lines to portray the shape

and elevation of the land.• Show natural features including mountains, valleys, plains,

lakes, rivers, and vegetation. • Identify the principal works of humans, such as roads,

boundaries, transmission lines, and major buildings.• Used for engineering, energy exploration, natural resource

conservation, environmental management, public works design, commercial and residential planning, and outdoor activities such as hiking, camping, and fishing.

Jekyll Island, Georgia

Topographic Maps

Using shading and detailed labeling, topographic maps show a lot of detail of land cover. This is a portion of the Carrollton map

Bathymetric Map (contours)

Bathymetric Map (colors)

Physiographic Map

• Using bathymetric data and artist’s perspective, this physiographic map of Iceland makes it easy to visualize the sea bottom

Nautical Charts

• Maps show you where to go, nautical charts show mariners “where not to go”

• Numbers are water depths in feet