C 17 Earths Interior Notes

Physical Geology Chapter 17 Earth’s Interior Notes Slide 2: Earth’s Interior is Important It affects what happens at _________________________where we live. It is difficult for us to see __________________________ inside Earth. We only study Earth’s interior through _____________________________________. We can’t go directly to the ____________________________________ to see what’s there. Slide 3: How do we know what’s inside Earth? How do we know Earth is not hollow? 1)We can learn about Earth’s interior by ________________ and deep ____________________________. However, the deepest mines are _____________ down and the deepest wells are ______________________________. Slide 4: 2) ___________________________, rocks brought up from below and incorporated in lava from volcanoes. These give us a clue as to what is __________________________. Slide 5: 3)______________________, pieces of rock from space that fall to Earth. They originate from the __________________________.

Possibly pieces of a former planet or a

_______________________________. Two types: __________________________ and __________________________________. See box 17.3 page 423. Slide 6: 4) Geophysics is the study of mechanical systems in Earth. Major areas of study include: a)______________________________ b)______________________________ c)______________________________ d) ______________________________

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Slide 7: Seismic Studies Geologist learn about Earth’s interior by studying _____________________________ from major _________________________ and ______________________________. It is a similar idea to using ________________________________ to see the inside of our bodies. _________________________________ have the ability to travel all the way through the ___________________________. Slide 8: Seismic Studies Seismic ______________________ and seismic __________________________ are both used to study the earth. _______________________________ is the way waves bounce off rock boundaries inside the earth. ________________________________ is the way waves bend as they pass through layers of different densities. Slide 9: Wave Travel Possiblities A. Seismic waves would travel ___________________ a hypothetical planet ________________________ properties along ____________________________ and at ________________________________.

B.

Wave _____________________ through a planet where velocity ___________________ with depth.

C. A few of the many possible ____________ that seismic rays take_________________ Earth. This shows there are different structures inside Earth.

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Slide 10: Seismic Reflection Scientists can measure the _____________ it takes for __________________________ seismic waves to reach a __________________________. From these data they can determine ______________________________________ in Earth. Slide 11: Seismic Refraction Waves ______________________ as they travel through Earth. They _______________________ or ___________________ as they enter or leave layers of different__________________________. As ______________________________ changes, the waves bend. Waves travel _______________________ through more ______________________ materials and _____________________ through less ___________________ materials. They __________________________ one way or another depending on whether they _________________________ up or ________________down. Slide 12: Seismic Refraction 1 _______________________ seismic waves in the lower velocity layer (________________________) reach the first two seismic stations before seismic waves that travel through the________________________________. However, . . . Slide 13: Seismic Refraction 2 . . . beyond _________________________, the first waves received passed through the ___________________, which is a zone of _____________________. These differences in travel times tell us Earth’s interior has___________________________. Slide 14: Earth’s Interior Has Three Major Subdivisions _____________________________ is very thin outer layer of the earth _______________________________is the thick “middle” shell of rock beneath the crust. ___________________ is the center of the earth.

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Draw and label Earth’s interior: layers, thicknesses, composition, densities.

Slide 15 Name the two types of crust:

Slide16: Continental Crust ____________________________ crust is the crust that makes up the continents for the most part. This crust is primarily “____________________________”.It is made chiefly of the minerals that make up ____________________________. The term “____________________________” is often used to describe the composition. (Silicon and aluminum). ____________________________l crust consists chiefly of granite, gneiss, and schist with a layer of ____________________________ rock on top. It ranges in thickness from ____________________________ km. Average thickness is 30 to ____________________________ km. It is thickest under the ____________________________. ____________________________travel at an average rate of 6 km/s. They go faster in the base of the crust due ____________________________. Average density of the continental crust is that of ____________________________, 2.7g/mL Slide 17: Oceanic Crust ____________________________crust is primarily the rock that makes up the ocean basins. It’s mainly ____________________________ on top grading to ____________________________ with depth. ____________________________is a term used to describe this rock: (silicon and magnesium). Average thickness is

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____________________________Km. Average seismic wave velocity is ____________________________ km/s. Average density is 3.0 g/mL. Slide 18: The Moho A boundary separates the crust from the ____________________________. This boundary is called the ________________________________________________________. (We’ll call it the ____________________________) At the Moho seimic velocities ____________________________ greatly. (Fig. 17.6) Slide 19: THE MANTLE The mantle is believed to be made of ____________________________for the most part. This is based on the velocities of seismic waves through the mantle ( 8km/s). The rock is believed to be ____________________________. (Fe, Mg, and lack feldspars). The uppermost rigid part of the mantle, combined with the crust, create a layer called the ____________________________. The plates are made of ____________________________. The ____________________________ is 70 to 125 km thick under the oceans, and up to 250 km??? under the continents.

Slide 20: Mantle Continued Below the lithosphere is

a

____________________________.

zone

in

This

the

mantle

where

low

velocity

zone

seismic is

waves

called

the

____________________________. Many think this is the zone where rocks are near ____________________________ or partially melted (like slush). The

____________________________

____________________________ ____________________________ ____________________________ Earth’s Interior Notes

may and

flow

of

plates

be:

1)the

2)

a

the

of

zone

mantle to

source allows

move.

much where

the

rigid The 5

____________________________ is about 200 km deep. 670 km is considered by some to be the ____________________________ between the upper and lower mantle. There are no ____________________________ below 670 km. (Figure 17.7) Slide 21: THE CORE There is evidence for a third major subdivision of Earth’s interior. Again seismic data are our eyes. It has been found that there is a region, between ____________________________ degrees from the epicenter, in which no ____________________________ are recorded. This area is called ____________________________. This is explained by ____________________________ refraction at the core boundary. (See Figure 17.8) ____________________________ causes waves to bend and creates a “shadow”. Slide 22: Core Continued There is also an ____________________________ shadow zone. This is a region where no ____________________________are detected. (Fig. 17.9) It begins at 103 degrees from the epicenter and 7 extends ____________________________ the world from there. It is caused because ____________________________ are not transmitted through the ____________________________ core. This suggests that the ____________________________ part of the core is probably ____________________________.

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Slide 23: More Core We see, therefore, that the core has ____________________________ layers: a liquid ____________________________and a solid ____________________________. The core is believed to be made of ____________________________with oxygen, silicon, and sulfur. ____________________________ range from about 10 to 13 g/mL We believe ________________________________________________________move in the mantle as well as in the____________________________. The two layers seem to stay separated due to ____________________________ differences. Slide 24: ISOSTASY ______________________is the balance of adjacent blocks of crust floating on the upper mantle. We can consider the crust as “______________________” on the mantle because of density differences. Fig. 17.11 shows how a block of wood will sink until it has displaced a mass of water equal to its mass (bouyancy). Slide 25: Two blocks won’t ____________________________ to the same depth if they’re different relative ____________________________. If we add ____________________________ to a block it will sink deeper into the water. If we remove ____________________________ from the block it will rise higher in the water. The depth of the block ____________________________ as it is loaded and unloaded with more matter. We believe the same happens to the ____________________________.

Slide 26: Isostatic Adjustment In simplest terms, we think the crust does the same thing. ________________________________________________________ is the vertical movement of crust to reach equilibrium. Mountain ranges have “____________________________”, therefore. This idea may help to explain some ____________________________ and ____________________________ in the crust.

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Slide 27: Crustal Rebound Areas loaded with____________________________or ____________________________ may show____________________________adjustment after the ____________________________ or ____________________________ is removed. (Scandinavia, Lake Bonneville) The uplift of the crust after removal of ____________________________is called ____________________________ rebound. Slide 28: Gravity Measurements Gravity measurements use Newton’s Universal Law of Gravity as the founding principle:

F is ____________________________, G is a constant, M is ____________________________, and D is the distance from the center of the two bodies. Gravity is affected with changes in either ____________________________ or ____________________________. Slide 30: Gravity Measurements Scientists use gravity meters (____________________________) to measure the gravitational ____________________________ for the earth. Slide 31: ____________________________ are used to measure gravity ____________________________ within the earth. A positive gravity anomaly means the gravity of an area is ____________________________ than normal. A negative gravity anomaly means the gravity of an area is ____________________________ than normal. Slide 32: What are some causes of gravity anomalies? 1)+ anomalies a) ____________________________forces are ____________________________ an area up. (mountain building) b) ____________________________ bodies

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2) - anomalies a) ____________________________ forces are holding an area ____________________________ (subsidence) creates anomalies at

the

____________________________. b)other causes of lower ____________________________ in the rock (caverns) Slide 33:

Slide 34: Slide 35: Slide 36:

Slides 37-45: Magnetic Field Studies We’ve already discussed magnetic fields, magnetic poles, magnetic reversals, normal polarity, reversed polarity, paleomagnetism, paleomagnetic reversals, and magnetometers. Be sure you review the terminology.

Slide 46: Magnetic Field Studies Magnetic studies reveal ______________________________ also. A _____________________________ magnetic anomaly is a reading of _____________________________ than normal magnetism. A_____________________________magnetic anomaly is a _____________________________ than normal magnetic reading. What do magnetic anomolies tell us?

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As with gravity, a deviation from average readings is called an _____________________________. A _____________________________ magnetic anomaly may be caused by a body of _____________________________ ore in a joint in limestone, which is nonmagnetic. A _____________________________ magnetic anomaly is caused by a down-dropped _____________________________ (a graben) in igneous rock. The graben may be filled with _____________________________ sediments where as the crystalline rocks on either side of the_____________________________may be highly _____________________________ due to magnetic minerals in the rock. Slide 47:

Slide 48:

Slides 49+: Heat flow also gives us evidence as to what earth is like inside. The __________________________________________________________is the rise in temperature with depth. Some areas have _____________________________ gradients than others. (magma, cooling rock, radioactive elements). Heat flow may indicate _____________________________and _____________________________in the mantle. High heat flow is generally associated with _____________________________ plate boundaries and hot v_____________________________. Low heat flow areas are associated with _____________________________ plate boundaries (trenches).

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