Earth Science – Chap. 2 – Sect.1

EARTH SCIENCE – CHAP. 2 – SECT.1

•OBJECTIVES•1 . L I ST T H E C HAR ACT ER IS T I C S O F EART H’ S T H R EE C O M PO S I T IO N AL ZO NES AND 5 ST R UC T UR AL ZO NES•2 . EX PL A I N H O W ST UDI ES O F SE I SM I C WAVES HAVE P R OV I DED I NFO R MAT I O N AB OU T EART H’S I NT ER I O R•3 . DEF I N E M AGN ET O SPH ER E AND I DENT I FY T HE PO SS I B L E S OU R C E O F EART H’S MAG N ET I SM•4 . SU MMAR I Z E NEWT O N’S L AW O F G R AV I TAT I O N

STATE SCIENCE STANDARDS

Recognize that the force of gravity keeps planets in orbit around the sun and influences objects on Earth and other planets (i.e., tides, ability of humans to move and function). Differentiate between an object’s mass and weight.

Investigate how thermal convection relates to movement of materials. Apply this knowledge in explaining the cause of movement of the Earth’s plates.

Describe energy sources, processes, and transformations of Earth materials as they progress through the rock cycle to form new sedimentary, metamorphic, and igneous rocks. Discuss how the cycling of rock is continuous.

EARTH STATS• Earth is not a perfect sphere• Earth is an oblate spheroid• Circumference around poles = 40,007 km• Circumference around the equator = 40,074 km• The spinning of the earth causes centrifugal

force, causing the poles to flatten and the equator to bulge

• Distance between highest mountain and lowest part of ocean = ~ 20 km.

• Average diameter of earth = 12,735 km.

OBLATE SPHEROID

HYDROSPHERE Earth cover by 71% water97% of that water is salt water3 % fresh water is in lakes, river,

streams, groundwater and frozen in glaciers and icecaps.

1% available for use by living organisms

All of earth’s water is know as the hydrosphere

HYROSPHERE

ATMOSPHEREThe gases in the earth’s

atmosphere supply oxygen to living organisms and shield the earth from harmful solar radiation

78% - nitrogen21% - oxygenLast 1% includes: CO2 , argon and

helium

CARBON DIOXIDE IN THE ATMOSPHERE

What does 400 ppm mean?.04% of atmosphere400 parts of Carbon Dioxide per 1

Million parts of atmosphereWhy is carbon dioxide so

important in today’s society?

LIVING ORGANISMS AND NITROGEN

Nitrogen is an essential component for life on Earth and makes up 78% of the atmosphere.

If humans need nitrogen to survive do we get t from the atmosphere like we get Oxygen?

If not, where do we get it?

NITROGERN-FIXING BACTERIA

PLANTS WITH NITROGEN_FIXING BACTERIA

LET’S EXPLORE NITROGEN_FIXING BACTERIA

With your partner gather some samples of clover from the A.I. Nature Area

Be careful to gently pull the plant from the ground preserving the root system

Locate the nitrogen-fixing bacteria nodules attached to the roots

Carefully place them onto a slide and observe them under a microscope

Make some observations in your notebooks!

EARTH’S INTERIORScientists use seismic waves to

speculate on the composition of earth’s interior

Seismic waves are vibrations that travel through the earth

Seismic wave studies have helped scientist determine that the earth is made up of three (3) major zones – compositional

(5) structural zones

EARTH’S LAYERS

COMPOSITIONAL ZONES OF THE EARTH

Crust: thin, outermost zone of earthMakes up 1% of earth’s massOceanic crust found beneath oceansBetween 5 and 10 km. ThickDenseComposed of mostly iron and magnesium

Continental crust makes up continentsBetween 15 and 80 km. Thick (thickest beneath mountain ranges)

Less denseComposed mostly of silicon and oxygen

COMPOSITIONAL ZONES CONTINUED

Mantle: zone below crustNearly 2,900 km thick (1,798

miles)Makes up almost 2/3’s of

earth’s mass

Core: below mantle and forms center of earth, made mostly of iron, makes up approx. 1/3 of earth’s mass

5 - STRUCTURAL ZONESLithosphere: the uppermost part of mantle and the crust. A rigid layer 15 – 300 km. ThickAsthenosphere: just below the lithosphere, approx. 200 km. Thick, plastic like (solid rock with ability to flow due to enormous temp. and pressure)Mesosphere: Below the Asthenosphere – solid rock-Approx. 2900 km

Outer core: dense, liquid layer about 2,250 km. Thick (1395 miles)Inner core: dense, solid sphere with a radius of 1,228 km. (761 miles)

SEISMIC WAVESPrimary waves (p-waves): travel through

solids, liquids and gases. Travel faster than s-waves

Secondary waves (s-waves): only travel through solids, slower than p-waves

Speed and direction of p and s waves affected by composition of material they travel through

Both waves travel faster through more rigid materials

THE MOHOIn 1909 Andrija Mohorovicic, a Croatian

scientist, discovered that the speed of seismic waves increases abruptly 32 to 70 km below earth’s surface. This change in speed marks the boundary between the crust and the mantle and is known as The Mohorovicic Discontinuity or simply The Moho.

The increase in speed indicates that the mantle must be denser than the crust.

ANDRIJA MOHOROVICIC- -THE MAN!

OTHER CHANGES IN WAVE VELOCITY

Approx. 100 km below the Moho the waves decrease in velocity at the boundary between the lithosphere and the less dense asthenosphere

Seismic waves increase in speed after this boundary until approx. 2,900 km.

At 2,900 km, p-waves slow down and s-waves disappear entirely. This marks the boundary between the mantle and the outer core (liquid)

At a depth of approx. 5,150 km (3,193 miles) the p-waves speed up again marking the boundary between the outer core and the inner core (dense solid)

SHADOW ZONESLocations on earth’s surface where neither

s-waves nor p-waves are detected (or where only p-waves are detected)

Caused by earth’s non-uniform composition of materials which causes the waves to bend and change direction due to speed differences of the waves

S-waves cannot travel through the liquid outer core and p-waves bend with different density materials forming shadow zones

SHADOW ZONE

EARTH AS A MAGNETEarth has two magnetic poles:The Northern Geomagnetic Pole and the Southern

Geomagnetic Pole with lines of force between the twoMagnetosphere: the area of space that extends beyond

the atmosphere that is affected by the magnetic fieldMagnetic field thought to be generated by the flow of

liquid iron in the outer core due to the conductivity of the iron producing electrical currents

Problem: the moon and sun both have a magnetic field but the sun has very little iron and the moon has no liquid core. This indicated that there may be some other force producing the magnetic fields.

EARTH’S GRAVITYGravity: the force of attraction that exists

between all matter in the universe, discovered by Sir Isaac Newton and described in his law of gravitation

Law of Gravitation: states that the force of two objects depends on their masses and the distance between them. The larger the masses of the two objects and the closer together they are, the greater will be the force between them.

EARTH’S GRAVITYThe mass of the earth exerts a force of

gravity that pulls objects toward the center of the earth.

Weight: the measure of the strength of the pull of gravity on an object. (measured in Newtons- on earth’s surface 1 kilogram of mass weighs about 10 N)

How much would a mass of 2-kg weigh?How much would a mass of 10-kg weigh?

WEIGHT AND MASSMass: the amount of matter in an objectWeight: the force of gravity on an objectMass of an object does not change with

location, weight doesThe weight of an object depends on its

mass and the distance from the earth’s center

An object would weigh approx. 0.3 % less at the equator than at the North Pole due to the difference in distance from the center of the earth.

QUIZ – CHAPTER 2, SECT 1

QUIZ

HOMEWORK

Read Chapter 2, sections 2 & 3Do section reviews 2.2 & 2.3- 1 – 12, 1 - 10

EXIT TICKET1.Would a person weigh more at the North

Pole or the Equator? Why?2.What is meant by 400 ppm? Why is it

significant in today’s society?3.Describe the Moho.4.Describe the difference between a “P”

wave and an “S” wave.