Chapters 14 and 15Chapters 14 and 15

Earth’s interiorEarth’s interior

EarthquakesEarthquakes

NASA at the Univ. of MissouriNASA at the Univ. of Missouri• In 1964 a telescope was installed a few

miles east of Columbia.• Students were contracted to point the

telescope at a particular place in the sky and open the shutter of a camera at a specific time. – WWB – National Bureau of Standards Radio

Station

• Photographs showed the flashes of a strobe on a satellite.

• Allowed the precise calculation of the location of the telescope.

In 1912, Alfred Wegener, a German meteorologist proposed that at one time all the continents were joined together.

Test questions from the videoTest questions from the video

• Tell several ways we know the surface of the earth is moving– At least one of the ways must be the magnetic

argument from the video– Key words whose meaning you will need to

know.• Plate tectonics• Lithosphere• Asthenosphere

• To check and see if your lowest test score and lowest lab are correctly removed from your average, do the following:

• 1) Circle the lowest lab and lowest test score on your printout.

• 2) Add 25 to the number of points possible on your lowest test and compare this to the last number in that row.

• 3) Add your points on the lowest lab to that of your lowest test and compare this to the last number in that row.

• If these numbers do not agree, write “check lowest scores” on the front page and return your printout.

Definitions you will need to knowDefinitions you will need to know

• Lithosphere

• Asthenosphere

• Crust

• Mantle

• Core

• Inner core

• fault

Sea floor SpreadingSea floor Spreading

Undersea Volcano Caught on CameraLarry O'Hanlon, Discovery News Undersea Eruption Dec. 4, 2007

22 million cubic meters (13,670 cubic miles) of new lava coming out of the East Pacific Rise -- a seafloor spreading center off the Pacific coast of Mexico.

50,000 Pictures were taken, some using the Alvin submarine

Lithosphere – movesLithosphere – movesAsthenosphere – softer rockAsthenosphere – softer rock

Plate boundaries – Mid-ocean Plate boundaries – Mid-ocean ridgeridge

Deep sea trenchDeep sea trench

Plate boundaries – sideways Plate boundaries – sideways motionmotion

Earthquakes – caused when Earthquakes – caused when tectonic plates shifttectonic plates shift

EarthquakesEarthquakes• Earthquake (Richter) Scale

– logarithmic scale

– An earthquake of magnitude 7 is 100 times larger than one of magnitude of 5

• 3 can be felt

• 6 significant damage

• Strongest earthquake measured so far = 8.7

• 15 large earthquakes/year

• 655,000 people died in China in 1976

Types of earthquake wavesTypes of earthquake waves

• Surface waves– Cause the most damage– Travel the slowest– Two types of surface waves

• Love waves– Back and forth shaking

• Raleigh waves– Like water waves

Types of earthquake wavesTypes of earthquake waves

• Body or interior waves– Go through the interior of the Earth– Two types of interior waves

• P – waves– Primary or pressure waves– Can pass through solids and liquids

• S – waves– Secondary or transverse waves– Cannot pass through a liquid

Primary or Pressure wavesPrimary or Pressure wavesFastest traveling wave

Will pass through both solids and liquids

Secondary wavesSecondary wavesSlower traveling body wave

Will only pass through solids

Love wavesLove wavesSlowest traveling earthquake wave

Does the most damage

Raleigh wavesRaleigh wavesSlowest traveling earthquake wave

Like water waves

Possible ways to predict Possible ways to predict earthquakesearthquakes

• Ian Browning– Earth’s tides due to sun and moon

• Electrical resistance• Gasses from deep wells• livestock uneasiness• tremors

– Fore shocks• Changes in the ionosphere• No reliable method has yet been found, many false

alarms have been given, only one real success (in China)

•Crust - thin•Mantle – occupies largest volume•Core (liquid)•Inner core (solid)

Earth’s internal structureEarth’s internal structure

• Crust– 0.5% of earth's radius – 5 km over oceans – On continents crust is between 35 km and

70 km (under some mountain ranges) thick• Mantle solid (soft)

– 80 % of earth's volume– 67% of mass

Earth’s internal structureEarth’s internal structure

• Core (outer or liquid core)– radius of 3470 km – 20% of earth's volume – Made of metal, mostly iron

• Far too hot for the iron to be magnetized• This means a current is flowing in the core

– source of earth's magnetic field• the axis of the core is tipped about half as

far as the earth itself. We are not sure why.• Earth’s magnetic poles have flipped at least

117 times in the last 76 million years

Earth’s internal structureEarth’s internal structure

• inner core

– Solid (because of the high pressure)

– Metal

– radius of 1390 km

– We know it is solid because the p-waves are reflected from it.

Earthquakes can be used to determine the internal structure of the Earth in the same way that x-rays do for the human body.

You will be asked to explain this on your test.

Internal temperatureInternal temperature• As you tunnel straight down, the temperature raises

one degree Celsius for each 35 m deeper you go.• Because the amount of heat energy the earth receives

from the sun is the same as it radiates to space, we know two things:– It is not still cooling off after its formation

• It has reached equilibrium• Some planets are still cooling off from their process of formation.

– It is not hot because of the sun’s energy

• Internal temperature of the Earth is between 3,000°C and 6,000°C

• It is hot because of the radioactive materials decaying in its interior.

Earthquakes – caused when Earthquakes – caused when tectonic plates shifttectonic plates shift

Areas in the US, most likely to have earthquakes. Missouri is among the states most likely to have an earthquake.

Earthquakes and volcanoes Earthquakes and volcanoes occur at the boundaries of occur at the boundaries of

tectonic platestectonic plates• Many earthquakes happen along the

boundaries of the tectonic plates.

• The list of earthquakes that happened in the last 7 days in the US is at http://earthquake.usgs.gov/eqcenter/recenteqsus/

New developments in Plate New developments in Plate Tectonics – The Farallon PlateTectonics – The Farallon Plate

• The Farallon plate is an ancient plate that began to slide under the west coast of North America as North America separated from Europe-Africa.

• The movement of this plate is responsible for the formation of the Rocky Mountains and all the volcanoes in the western US.

• In the summer of 2008 I joined a group that studied some of these volcanoes.

The Farallon plate moves under the North American plate forming the Rocky Mountains and the volcanoes on the western US. A NASA/Goddard animation.

Published by AAAS

L. Liu et al., Science 322, 934 -938 (2008)

Fig. 2. Observed and predicted continental flooding and borehole subsidence for

different temperature scaling and mantle viscosities

Volcanoes of North America – Note how the volcanoes outline the shape of the Farallon tectonic plate.

Summer 2008Volcano Safari, Albuquerque, NM

At the entrance to a lava tube.

Inside the lava tube.

Wildlife and petroglyphs

Be sure you understand this figure, you will be given a similar one on the test with some of the numbers blank. You will fill in the missing numbers. Memorizing the numbers will do no good as the ones on the test will be different. The relationships are what is important.

Be sure you understand this figure, you will be given a similar one on the test with some of the numbers blank. You will fill in the missing numbers. Memorizing the numbers will do no good as the ones on the test will be different. The relationships are what is important.

Why? (Global warming)Why? (Global warming)The energy stream. All the energy that hits the Earth from the sun flows down this river then goes back to space.

Methane is to carbon dioxide as concrete is to dirt. A bigger dam needs less concrete. Less methane produces more global warming.

Carbon dioxide is like an earthen dam, it takes a lot of dirt to make a good dam.

sun

space

The greatest effect of global The greatest effect of global warming on your life will be:warming on your life will be:

• Your pocketbook – Cost of power– Cost of food– Cost of storms

Unanswered questionsUnanswered questions

Exactly what conditions will make the ocean currents change? What is the “tipping point”.

When will this happen?If the permafrost thaws, how much methane

will be released?What will be the effect of this methane on the

climate? We know it will greatly increase global warming

How will each part of the Earth will be affected by global warming? Most models predict our region (the Midwest) as

becoming a much dryer.

• Labs for this week will be to study seismograms of earthquakes to determine how far the earthquake happened from the place the seismogram was recorded.

• To do this we need to distinguish between two types of earthquake waves, primary or P waves and secondary or S waves. The P waves travel faster and arrive sooner. The distance between the P and the S waves tells us how far away the earthquake was.

Primary or Pressure wavesPrimary or Pressure wavesFastest traveling wave

Will pass through both solids and liquids

Secondary wavesSecondary wavesSlower traveling body wave

Will only pass through solids