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					Time For Some More Geology!

Once Again It Is Time For…
• The “Nutcase Conspiracy Theory” of the day!

The Martians Are Calling!
• “The Face On Mars” • Here is a famous image taken by the Viking orbiter. The way the shadows fall over this hillside gives the strong impression of a face.

The Martians Are Calling!
• NASA claims the hillside is a natural formation. The “face” is merely a trick of shadow. • The conspiracy theorists believe NASA is hiding evidence of a Martian Civilization.

The Martians Are Coming
• Some conspiracy theorists believe it is a cosmic gesture of “welcome and goodwill” (kinda like the statue of liberty). • Others think it is actually a massive monument depicting a Martian’s face. • And there are MANY other “theories” that are wilder still…

Those Crazy Martians
• Here’s the truth. • It’s not a face. It’s not even artificial. But it is a very *real* effect. • Instantly and easily recognizing faces is a very important skill for humans. Our brains are wired to be very good at it.

Here is a very fuzzy, very poor quality picture of a real face, yet you probably instantly recognized it was a human face.

Those Crazy Martians
• Our brains are literally wired to see faces in any pattern that even vaguely resembles a face: clouds, fogged shower doors, grease smears, potato chips, tortillas, and on and on. • It would actually be *more* of a surprise if there were no natural rock formations on Mars that looked like faces, given how readily we see them when they’re not even there.

The Face, Debunked
• Need more convincing? • Here’s the face, taken close up, with a much better camera, under different lighting conditions. • Does it still look a little like a face? Sure! But it’s obvious that it’s a natural rock formation, not a giant sculpture.

The “Lost Civilization”
• But it doesn’t even end there, for the conspiracy theorists are very adamant! • They claim there is a lot more evidence of a lost Martian civilization. • We’ll look at this evidence in more detail next time.

And Now, Back To The Earth

Metamorphic rocks
• Rocks formed by the interaction of pressure, temperature and magma within the Earth. • As rocks are deeply buried they are deformed and new minerals recrystallize at the elevated temperatures and pressures to form metamorphic rocks.

Common Metamorphic Rocks
• Slate rocks are produced from the sedimentary rock Shale.
– Form at (relatively) low temperatures.

• Schist rock is also formed from Shale.
– Form at (relatively) high temperatures.

Common Metamorphic Rocks
• Gneiss is formed under a very high temperature process, with nearly any rock as the starting point.

Limestone and Quarts Metamorphism
• These rocks consists of single minerals • High temperature and pressure cannot change these rocks into different rocks • BUT the metamorphic process can change the crystal structure
– LIMESTONE BECOMES MARBLE – SANDSTONE BECOMES QUARTZITE

Understanding the inside of the Earth
• It is impossible (so far) for humans to see very far beneath the surface of the Earth
– So, the details of the structure INSIDE the earth must be studied in some other indirect way

• One of the most powerful tools used to understand the interior of the Earth is analysis of the motion caused by

EARTHQUAKE WAVES

Earthquakes
• This is the general term given to the vibrations (or sudden movements) of the Earth’s crust.
– Earthquakes generally occur over a very short time scale, ranging from only a few seconds to a few minutes – But even in a few seconds, great destruction can result

Earthquake notes
• Most earthquakes are the result of a sudden shift of rocks that are located within the first 70km beneath the surface • Most earthquake activity occurs along defined fracture lines called FAULTS

Earthquake notes
• The shifting occurs only after significant strain energy is built up within or between rock structures • The sudden shift is actually a release of this built up energy

Visualize:
• Imagine holding a ruler.
– Grab each end and bend slowly. – As you bend, you are building up elastic energy in the ruler, and the strain on the material in the ruler increases. – When the strain gets too great, the ruler snaps in two (a sudden movement), and the built up elastic energy is released.

The power of the QUAKE
• Most of you have heard the term RICHTER SCALE
– it describes the power of an earthquake

• But what exactly is the RICHTER SCALE?

The Power of the QUAKE
• a numerical measure of earthquake “size” • determined from the

logarithm of the maximum displacement
of the earthquake signal as seen on the seismogram

RICHTER SCALE
• Devised in 1935
– originally devised to compare the magnitudes of earthquakes in California – has been adopted world-wide.

• The value calculated reflects

the amount of energy released.
• The Richter scale ranges

from zero to 8.9
– (the largest recorded, Chile 1960).

What does “LOGARITHMIC SCALE”MEAN? 6 And so on
•
x FACTOR OF 10000 On (order of magnitude larger) a logarithmic scale x FACTOR OF 1000 (order of magnitude larger) FACTOR OF 100 – eachxinteger increase of magnitude is(orderFACTOR OF 10 a factor of 10 larger) x (order of magnitude larger)

5 4
3

2
1

Start here

0

So, an earthquake of 6.0 is 10 times more severe than one of 5.0, one of 7.0 is 100 times more severe than 5.0

WHY A LOGRITHMIC SCALE
• Logarithmic scales are used
– whenever a LARGE RANGE of values is to be represented

• Many physical situations are measured on logarithmic scales
– pH scale – Sound : decibel scale (dB)
• based on the huge range of human hearing

FAULTS
• These “cracks” in the CRUST are found in rock formations of all kinds • Some are due to molten rock contracting as it cools • Others may be due to mechanical stresses in the crust

FAULTS
• While scientists can identify faults, prediction of an earthquake is nearly impossible • There are frequently no obvious warning signs

EARTHQUAKE LINGO

• Focus:
• The point where an earthquake starts –where the movement actually occurs • often many kilometers deep within the earth.

• Epicenter:
• The point at the surface directly above the focus is called the earthquake epicenter.

Layers of Earth
• At the moment the earthquake occurs, some of the energy released by the sudden motion of the rocks is transmitted in all directions from the fault in the form of waves

Layers of Earth
• The waves travel either on the surface
– SURFACE WAVES

• Or through the interior of the Earth
– BODY WAVES

Figure 14-27
• Body waves
– S – Wave – P – Wave

• Surface waves
– LOVE WAVE – RAYLEIGH WAVE

Two types of body waves
• Compressional waves
– also known as primary or “P” waves – travel fastest, at speeds
• between 1.5 and 8 kilometers per second

• Shear waves
– also known as secondary or “S” waves – travel more slowly
• usually at 60% to 70% of the speed of P waves

Announcements
• Quiz Next Time! • Today’s topic: What Earthquake Waves Tell Us About The Earth’s Interior. • But First…

Once Again It Is Time For…
• The “Nutcase Conspiracy Theory” of the day!

More Mars Silliness…
• The Face on Mars is on one edge of the Cydonia Planitia – “The Plains of Cydonia.” • Here’s is a pseudo3D image of the region:
I found this one at www.mufor.org

More Mars Silliness…
• Here’s the face: • The “Face Believers” believe these features on Cydonia are the ruins of Martian cities: • They contend NASA heads a conspiracy to hide evidence of past intelligent life on Mars.

• A chief proponent of the “Mars conspiracy” is Richard Hoagland. • He claims to see structures in Mars photos when you magnify them and look carefully at the results. • He also claims that the “buildings” of Cydonia are arranged using angles only intelligent beings would have known about. Here’s an example:

More Mars Silliness

Image taken from www.badastronomy.com, which in turn took the image from Hoagland’s web site.

Intelligent Angles
• The angles indicated certain are close to significant values (such as pi or Napier’s constant of e). • Here’s the problem:
– If I draw three random dots, and draw a line from each dot to its two neighbors, I’ll form three angles (a triangle, actually). – If I add just one more random dot and draw lines connecting each dot to all the others, I’ll form 16 angles!

Intelligent Angles
• Each added dot dramatically increases the number of angles I can draw. • In searching for his angles, Hoagland used seventeen different “structures” – the number of potential angles was utterly staggering! • Statistically it would actually be quite a surprise if a few dozen didn’t just happen to be fairly close to “significant numbers” like pi.

The Mars Conspiracy
• There’s more. Here’s an example of an image from Hoagland’s website (www.enterprisemission.com) • Hoagland claims this looks like “excavated Anasazi Great Houses here in the American Southwest.” • First off, the formations don’t even look unnatural. • Second, the picture (and most on his website) are horribly overprocessed, which creates odd artifacts and features in the images themselves.

The Mars Conspiracy
• We could go on and on, but we just don’t have time. • A simple search of the web will give you more information than you ever wanted to know about this topic. If it interests you, then go for it!

Earthquake Waves and Earth’s Interior

Body Wave Review
• Compressional waves
– also known as primary or “P” waves – travel fastest, at speeds
• between 1.5 and 8 kilometers per second

• Shear waves
– also known as secondary or “S” waves – travel more slowly
• usually at 60% to 70% of the speed of P waves

Using waves to study Earth’s Interior
• The speed of the waves is determined by what kind of material they passed through. • Analysis of where and how the waves arrive at other points on the earth have helped scientists to understand that the interior of the Earth is NOT uniform

Understanding waves
• There are certain locations on earth where no P waves are deteced, no matter where the earthquake itself occurs • These locations are known as SHADOW ZONES

S-P Waves and Shadow zones
Shadow Zones

What waves tell us
• Scientists have concluded that the earth’s interior can be considered as begin divided into three regions.

What waves tell us
• At the center of the earth lies a central CORE • Surrounding the CORE is a large region called the MANTLE • Finally, the surface of the earth is called the CRUST

The CORE
• The average density of the earth is about twice that of the average density of rocks that lie on the surface • This leads to the conclusion that the materials inside the earth must be very dense

The Earth’s Core
• Due to the idea that the core at the center of the earth must be very dense, scientists have concluded that the inner core is most likely composed of iron in a solid state. • This conclusion is based on the estimation of the pressure and temperature likely to be found at the center of the earth

The center of the core
• Outside of the inner core, the decreasing pressure drops the melting point below the temperature. So the outer core is most likely liquid. • The mantle is semi-solid: it flows like a soft, partially melted plastic.

The center of the core
• It is certain that the interior of the Earth is very hot, based on the rate at which heat flows outward from the interior

• Most of the heat generated in Earth’s interior is a result of radioactive elements such as uranium

The interior structure
• Seismographic studies have led scientists to this overall picture of how the interior of the earth is structured


				
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