unit c: key the changing earth - ms. mogck's classroom€¦ · unit c: key the changing earth...

K.Mogck Science 20 2017

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Unit C: KEY

The Changing Earth



Important Notes



Topic 1: Early Earth

Term Definition Precambrian Era

Outcrop

Core

Mantle

Asthenosphere

Mesosphere

Lithosphere

Crustal Plate

Paleomagnetism

Sedimentary Rock

Fossil

Strata

Stromatolite

Cyanobacteria

Trace Fossil

Photosynthesis



Scientists are unable to directly observe the layers below the lithosphere, so they use indirect evidence from events, such as earthquakes, to assist in developing theories about Earth’s structure.



One theory is the idea that it is nuclear decay deep within the core that provides much of the heat energy needed to drive the flow of material in the mantle. Scientists believe that enormous convection cells within the mantle push and pull on the Earth’s crustal plates, driving the idea of plate tectonics.

Plate tectonics are additionally supported by the idea of paleomagnetism. Researchers found that sections of the sea floor have rocks with their magnetic fields pointing in opposite direction, indicating that the magnetic field of the earth has reverse more than once in the past several million years.



The world’s oldest evidence of earth dates back 3.8 billion years. (Life may have existed previously, however there is no fossil evidence… yet…) Early Earth was a hostile place, with frequent volcanic eruptions, poisonous gases, extreme climates and little oxygen. Scientists have discovered that certain types of bacteria called Archaea thrive in these environments by feeding on hydrogen sulfide (H2S). Fossil evidence in the form of stromatolites indicates that cyanobacteria grew and died, layering calcium carbonate (limestone) on top of each other. The cyanobacteria were one of the single producers of oxygen. Cyanobacteria may have been the first organisms to use chlorophyll to trap the Sun’s energy and perform photosynthesis.

Formula for Photosynthesis:

By the end of the Precambrian Era, cyanobacteria had transformed the atmosphere, leaving behind stromatolite mounds and banded iron deposits as indirect evidence of their existence. Direct evidence such as fossils revealed that stromatolites shared their shallow waters with multicellular creatures like jellyfish, worms and early plants.



Practice Problems:

1. Identify the first major section of time in Earth’s history. Describe when it began and when it ended.

PRECAMBRIAN = 4.6 billion years ago 590 million years ago

2. Sketch a simple labelled diagram showing a cross section of Earth.

3. A lava lamp is a good model of Earth’s convection currents. The semi-fluid material

inside the lamp could represent the mantle. The heat source could represent the heat from the Earth’s core. Explain how a lava lamp works and apply it to plate tectonics.

As the wax heats up (by the light bulb) in a lava lamp, the molecules become less dense and rise to the top of the lamp. As the cool down, they again become more-dense and drop to the bottom of the lamp, where they can be reheated. This creates a convection current, similar to the molten mantle in the earth.

4. Name and describe Earth’s first living creatures.



Cyanobacteria – single celled organisms that lived on hydrogen sulfide and performed photosynthesis.

5. How old are the earliest signs of life?

As of March 2017, the earliest sign of life dates back to 4.28 billion years ago.

6. Describe the environment in which Earth’s first creatures lived.

Very hostile – high temperatures, many volcanic eruptions and earth quakes. The atmosphere contained a lot of H2S and was not oxygenated.

7. While hiking in Cameron Falls in Waterton National Lakes Park, Ms. Mogck finds sedimentary layers of limestone known only to be deposited in warm seas. What do these limestone deposits indicate?

Limestone indicates the presence of previously existing cyanobacteria. As the bacteria died, they fell to the bottom of the ocean and were compressed into CaCO3. This eventually compressed into limestone.



Topic 2: Fossils and Relative Time

Term Definition Law of

Superposition Relative Dating

Stratigraphic

Sequence Intrusion

Absolute Age

Index Fossil

Uniformitarianism

Unconformity

Rock Cycle

Radioactivity

Radioactive Decay

Half Life

Isotope



Law of Superposition (Relative Dating)

OLDER FOSSILS WILL BE LOWER DOWN IN THE ROCKS, AS TIME

WENT ON LAYERS WERE ADDED.

An exception to the law of

superposition can occur when large, underground bodies of magma force hot molten rock to invade cracks found in the sedimentary rock. This invading rock is called an intrusion. William Smith (1769-1839) noticed that certain distinctive fossils kept re-appearing at various locations. Further, these distinctive fossils always appeared in the same order within the layers of rock at all locations. These distinct fossils acted like an index; they establish a common time of origin for widely dispersed rock layers.



During the 19th century, geologists used index fossils to assemble a generalized relative time scale for all of Earth. The Geological Time Scale is divided into 4 major eras: Precambrian, Paleozoic, Mesozoic and Cenozoic. A massive disappearance of fossils and an unexplained appearance of new fossils mark the boundary between each era. Each era is broken down into smaller divisions called periods. In some cases, periods are broken down into epochs.



Practice Problems: 1. Look at the fossilized shark tooth to the left. How could undamaged solid shark teeth become embedded in sedimentary rock, which is also solid?

Shark’s tooth fell out and then was covered by dead organisms and sand and compressed over time.

2. Create an if, then, because hypothesis about which was deposited first, the shark teeth or the strata below the shark teeth. Remember, as good hypothesis requires a reason!

If the shark’s tooth is newer (younger) than the strata, then the shark’s tooth will be on top of the strata because of the law of superposition which states that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it.

3. Research and summarize the contributions of Nicolas Steno and William Smith to the field of geology.

Steno – Law of Superposition, Principle of Original Horizontality, Principle of Lateral Continuity, Principle of Cross-Cutting Relationships Smith – Strata in relative positions

4. List the four eras of the Geological Time Scale.

Precambrian Paleozoic Mesozoic Cenozoic



5. Describe the criteria geologists use to divide the Geological Time Scale into eras

A massive disappearance of fossils and an unexplained appearance of new fossils mark the boundary between each era. Each era is broken down into smaller divisions called periods. In some cases, periods are broken down into epochs.

6. Identify with period is more recent:

a. Triassic or Permian

b. Jurassic of Precambrian

c. Devonian or Pennsylvanian

d. Carboniferous or Cretaceous

7. Which epoch are you living in?

Holocene

8. The last ice age was called the Pleistocene Ice Age. Identify the period in which it appeared.

Quaternary Period in the Cenozoic era



Topic 3: Pinpointing Time

Term Definition Uniformitarianism

Unconformity

Rock Cycle

Radioactivity

Radioactive Decay

Half-life

Isotope

Parent Isotope

Daughter Isotope

James Hutton (1726-1797) believed that in order to unlock the mysteries of the past, you must understand the processes at work in the present. Hutton’s work is considered the birth of modern geology. Hutton travelled and observed rock strata throughout Scotland, and applied the Law of Superposition to the rocks, and eventually recognized that erosion caused unconformity in the rocks he was observing. Hutton proposed that the geological process of Earth operates as a self-sustained system.



Rock Types - INQUIRY

Type of Rock How Formed Where Formed Example

Sedimentary

Igneous

Metamorphic



During the 19th Century, it was discovered that isotopes of certain elements emitted rays invisible to the eye. Marie Curie named this property radioactivity.

While working at McGill University (in Montreal), Ernest Rutherford discovered that energy emitted from radioactive materials was in the form of high-speed particles. He was also able to measure the intensity of this radiation by determining the number of particles emitted per second.



Radioactive Decay Rutherford discovered a remarkable property of radioactive material: the intensity decreased by ½ in a constant increment of time. Working with Radon-222, he determined that every 55.6 seconds, the intensity was 50% it’s original. He also determined that radon-222 was unstable, and spontaneously changed into the more stable polonium. Example: Radioactive decay of Radon-222 into Polonium

Radioactive Dating

Because radioactive decay of an element occurs at a fixed rate of time (half-life) the decay process can be used to measure the time passed since a rock or fossil has formed. Scientists now use a mass spectrometer to count the number of atoms and their isotopes present in a sample. Carbon-14 is a rare isotope of carbon that starts out as regular, non-radioactive nitrogen-14. Making its way into the food chain through photosynthesis, when an organism dies and the organisms’ remains are preserved, the date can be measured using the amount of carbon-14 remaining. Example Equation: Radioactive decay of Carbon-14 into Nitrogen-14



Absolute Age To calculate the age of a fossil, we will need to compare the % of original unstable atom (parent isotope) to the % of more stable product (daughter isotope). You will need to use the information provided on p. 8 of your data booklet

Example 1 A rock has been found to contain uranium-238 (U-238) and lead-206 (Pb-20). If 60% of the U-238 has changed to Pb-206, how old is the rock? Step 1 Determine the parent and daughter nuclides. Parent is the original unstable atom, while daughter is the product atom (what it changes into to become more stable). Parent: uranium-238 Daughter: lead-206 Step 2

If necessary, determine the % of parent nuclide that remains in the sample. The parent % and the daughter % need to add up to 100%. Here, we know that the daughter accounts for 60%, which means there is 40% left to make 100%.

(100% total) – (60% daughter) = 40% parent

There is 40% U-238. Step 3 Use the decay curve on p. 8 to find how many half-lives have elapsed when there is 40% of the parent. Based on the curve, about 1.3 half-lives have happened. Step 4 Still on p. 8, look up the half-life for the element you are dealing with. We are looking for U-238, which has an approximate half-life of 4.47 x 109 years. (a is the unit for years) Notice that this table also shows you what each parent nuclide will turn into. Carbon-14 will turn into nitrogen-14; potassium-40 will turn into argon-40; etc. Step 5 Multiply the length of one half-life by how many half-lives have gone by.

(4.47 x 109 a) x (1.3 half-lives) = 5.811 x 109 a Finally, round your final answer to three digits: 5.81 x 109 a (5.81 billion years old)



Practice Problems:

1. How does each of the main rock types form?

Sedimentary = small pieces of rock crushed together under pressure Metamorphic = heat and pressure of sedimentary rock Igneous = rock becomes super-heated from the Earth’s core and melts into magma which is cooled into rock

2. Describe the oldest rocks in Canada. What type are they?

Igneous rock in the Canadian Shield

3. Why does radioactivity make a good clock?

Radioactive decay occurs at a constant rate, specific to each radioactive isotope.

4. Describe what radiometric method is used to date organic remains. Explain how this science works.

Scientists now use a mass spectrometer to count the number of atoms and their isotopes present in a sample. Carbon-14 is a rare isotope of carbon that breaks down into Nitrogen-14. By measuring the amount of remaining carbon-14, scientists can determine the age of organic material.

5. A geologist determines the percentages of uranium-238 and lead-206 found in a zircon. She finds that 30% of the sample is lead-206. Determine the age of the zircon.

Lead-206 = 30% Uranium-238 = 70% (0.6 half-lives)

0.6half-lives x 4.47x109 = 2.682x109 years old 6. A sample of orthoclase is date using potassium-40. A mass spectrometer analysis shows

that 20% of the potassium-40 is present in the sample. Use this data to determine the age of the orthoclase sample.

Potassium-40 = 20% = 2.3 half-lives



2.3half-lives x 1.26x109 = 2.898x109 years old

7. The oldest moon rock ever dated contains 6% of the daughter nuclide strontium-87. Use this information to determine the minimum age for the rock.

Daughter Strontium-87 = 6% Parent Rubidium-87 = 94% = 0.15 half-lives

0.15half-lives x 4.88x1010 = 7.32x109 years old

8. Volcanic ash deposits can be dated using uranium. About 100 million years ago, a series of volcanic eruptions blanketed Alberta with ash, which now form layers known as the Crowsnest Volcanics. Work your way backward to determine the percentage of uranium-235 present in the Crowsnest Volcanics.

100 000 000 years old = ??? half-lives x 7.04x108 = 0.142 half-lives

using the graph = 38% uranium remaining

9. The frozen body of a hunter was found in 1991 by two hikers. Carbon-14 dating methods found that the body contained 52.5% of the original carbon-14 that would have been present in his body at his time of death. Determine the age of the ice mummy.

Carbon-14 = 52.5% = 1.2 half-life

1.2half-lives x 5.73x103 = 6876 years old



Topic 4: Geological Disasters

Term Definition Fault

Subduction

Focus

Epicentre

Primary Waves (P-

waves) Secondary Waves

(S-waves) Amplitude

Longitudinal Wave

Transverse Wave

Richter Magnitude

Tsunami

Pangea

Cordillera

Here’s What So What? Now What?



How does this occur? What is the cause?

Geological and Atmospheric results due to the disaster.

What happens?

Earthquake

(s-waves) (p-waves)

An earthquake is what happens when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter. The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air. P waves are also known as compressional waves, because of the pushing and pulling they do. Subjected to a P wave, particles move in the same direction that the wave is moving in, which is the direction that the energy is traveling in, and is sometimes called the 'direction of wave propagation'. The second type of body wave is the S wave or secondary wave, which is the second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium. It is this property of S waves that led seismologists to conclude that the Earth's outer core is a liquid. S waves move rock particles up and down, or side-to-side--perpendicular to the direction that the wave is traveling in (the direction of wave propagation)

Plate shifting and grinding cause quakes that damage structures and endanger human life.

Volcano

Volcanoes form when magma reaches the Earth's surface, causing eruptions of lava and ash. They occur at destructive (compressional) and constructive (tensional) plate boundaries.

1. Magma rises through cracks or weaknesses in the Earth's crust. 2. Pressure builds up inside the Earth. 3. When this pressure is released, eg as a result of plate movement, magma

explodes to the surface causing a volcanic eruption. 4. The lava from the eruption cools to form new crust. 5. Over time, after several eruptions, the rock builds up and a volcano forms.

Formation of new rocks and possibly islands Release of toxic gas H2S and CO2 Release of ash that may affect the climate

Tsunami

Most tsunamis are caused by earthquakes generated in a subduction zone, an area

where an oceanic plate is being forced down into the mantle by plate tectonic forces. The friction between the subducting plate and the overriding plate is enormous. This friction prevents a slow and steady rate of subduction and instead the two plates become "stuck." As the stuck plate continues to descend into the mantle, the motion causes a slow distortion of the overriding plate. The result is an accumulation of energy very similar to the energy stored in a compressed spring. Energy can accumulate in the overriding plate over a long period of time - decades or even centuries. Energy accumulates in the overriding plate until it exceeds the frictional forces between the two stuck plates. When this happens, the overriding plate snaps back into an unrestrained position. This sudden motion is the cause of the tsunami - because it gives an enormous shove to the overlying water. At the same time, inland areas of the overriding plate are suddenly lowered. The moving wave begins travelling out from where the earthquake has occurred. Some of the water travels out and across the ocean basin, and at the same time, water rushes landward to flood the recently lowered shoreline.

Rising ocean levels

Plate shifting and grinding create new geological

structures

http://geology.com/nsta/convergent-plate-boundaries.shtml

http://geology.com/plate-tectonics.shtml



The fossil record contains evidence of 6 mass extinctions. The end of the Permian Period 250 million years ago is marked by the greatest extinction of life in the fossil record. It occurred at the end of the Paleozoic era, at this time about 70% of land animals became extinct, as well as 90% of the ocean species. Research and discuss 4 possible reasons for these mass extinctions. Which do YOU think is the best reason? Catastrophic methane release Catastrophic methane release has been suggested as a possible cause of mass extinction. Methane clathrate is an ice-like substance formed from water and methane in the sea bed, arctic lakes and permafrost. Flood basalt eruptions Flood basalt eruptions are a type of large-scale volcanic activity, both in terms of extent and duration, that can occur on land or on the ocean floor. A flood basalt may continue to erupt for tens of thousands - possibly millions - of years and the lava can cover hundreds of thousands of kilometres. Climate change Earth's climate is not constant. Over geological time, the Earth's dominant climate has gone from ice age to tropical heat and from steamy jungles to searing deserts. Impact events Impact events, proposed as causes of mass extinction, are when the planet is struck by a comet or meteor large enough to create a huge shockwave felt around the globe. Widespread dust and debris rain down, disrupting the climate and causing extinction on a global, rather than local, scale.

http://www.bbc.co.uk/nature/extinction_causes/Clathrate_gun_hypothesis

http://www.bbc.co.uk/nature/extinction_causes/Clathrate_gun_hypothesis

http://www.bbc.co.uk/nature/extinction_causes/Flood_basalt

http://www.bbc.co.uk/nature/extinction_causes/Geologic_temperature_record

http://www.bbc.co.uk/nature/extinction_causes/Impact_event



Practice Problems:

1. Why do urban areas usually suffer the greatest loss of life as a result of earthquakes?

Many people and structures in a condensed area

2. Sketch 2 diagrams that illustrate the difference between S-waves and P-waves.

3. Identify which type of seismic waves produces the most damage in an earthquake

S waves = shorter with higher amplitude

4. Why are trilobites an excellent index fossil for the Paleozoic Era?

A good index fossil is one with four characteristics: it is distinctive, widespread, abundant and limited in geologic time.

5. Identify 4 of the possible causes of the Permian Extinction

Methane, Flood, Climate Change, Catastrophic event



6. Describe the 2-types of plate boundaries often characterized by volcanic activity

Divergent and Convergent plate boundaries

7. Consider the following statement: It was a mass extinction that gave dinosaurs an opportunity to flourish, and it was a mass extinction that marked their demise. Explain this statement.

Dinosaurs began to flourish because there were no major predators and thus they grew and dominated. They were also wiped out by a mass extinction.

8. Explain how the Cretaceous/Tertiary Mass Extinction created an opportunity for the

rapid diversification of mammals.

Competitors and predators of mammals disappeared, removing the limitations on what mammals could do. They immediately began to increase in body size and ecological diversity. Mammals evolved to a greater variety of forms.

9. Briefly explain the importance of the Burgess Shale Fossils

The Fossils. The Burgess Shale is famous for its exquisite fossils of soft-bodied organisms. It is exceptional to find complete animals preserved, especially ones that had only soft tissues and no mineralized structures. (Typically it is only the hard parts of organisms - shell or bone - that become fossils.)



Topic 5: Climate Change

Term Definition Cenozoic Era

Glacier

Continental Ice

Sheet Mountain Glacier

Ice age

Glaciation

Weather

Climate

Hydrosphere

Global Conveyor

Cause

Correlation

Probability

The Cenozoic Era (65million years ago – present) is the last of the era’s in Earth’s history. It is divided into 2 periods: Tertiary and Quaternary Period.



The relentless movement of the tectonic plates resulted in the formation of the Rocky Mountains, and the migration of North America towards the north pole, which cooled the climate drastically. During the first 1.5million years of the Tertiary period, there was a significant drop in the average global temperature, changing animals and plants. Tropical rain forests gave way to evergreen forests with rivers, lakes and swamps. Mammals diversified and flourished, due to the dominance of grasses . By the end of the Tertiary Period, the climate became so cold that snow began to accumulate in polar regions, eventually creating glaciers. What adaptations do you think animals started to exhibit due to these newly formed glaciers and colder temperatures? Why? Fur or feathers, adapting their actions to building nests and burrowing. Thick layers of fat, hibernating over the long winter months to avoid the cold. White fur for camouflage in the snow. The many retreating glaciers and ice sheets around the world may be indicators of a warming trend in recent years, which may lead to rising sea levels and fresh water shortages.



Practice Unit Test

1. Oceanic crust and the continental crust make up the layer of the Earth called the

a. Asthenosphere b. Lithosphere c. Mesosphere d. Stratosphere

2. Which of the following creates pushes and pulls on Earth’s crust that cause it to crack,

tear and move?

a. Evaporation b. Subduction c. Paleomagnetism d. Convection currents

3. The correct order for the eras from the oldest to youngest is

a. Cenozoic, Mesozoic, Paleozoic, Precambrian b. Mesozoic, Paleozoic, Cenozoic, Precambrian c. Precambrian, Paleozoic, Mesozoic, Cenozoic d. Precambrian, Cenozoic, Mesozoic, Paleozoic

4. The Law of Superposition states that

a. All rocks and fossils in a given area are the same age. b. For a given sequence of rock layers, any layer is younger than the one beneath it. c. All rock layers consisting of the same type of rock are the same age. d. A sequence of rocks is the chronological record of a given region.

5. A fossil that can be used to correlate rock layers in different locations is a(n)

a. Historic fossil b. Stratigraphic fossil c. Index fossil d. Relative fossil



6. The era that spans the greatest number of years in Earth’s geological history is the

a. Mesozoic b. Cenozoic c. Precambrian d. Paleozoic

7. Which of the following is a characteristic of a good index fossil?

a. It is easily recognizable b. It appears only briefly in the geological record c. It has a wide geographical distribution d. All of the above are correct

Use the following diagram to answer the next question.

8. In the diagram above, the layers from youngest to oldest are

a. A, B, C, D, E, F b. A, C, B, D, F, E c. F, E, D, C, B, A d. F, D, E, C, A, B

9. In a typical rock sequence, an intrusion must be

a. Older than the rock layers it cuts into b. Younger than the rock layers it cuts into c. The same age as the rock layers it cuts into d. The age of the rock doesn’t matter



10. The process in which the nucleus of an unstable atom disintegrates and causes the atom to become a new element is known as

a. Unconformity b. Carbon dating c. Radioactive decay d. Half-life

11. The type of seismic wave that travels with the greatest speed and causes solid rock to

compress and expand is

a. a shear wave b. a primary wave c. a secondary wave d. an electromagnetic wave

Use the following information to answer the next question.

12. On the diagram above, subduction is shown at location

a. 1 b. 2 c. 3 d. 5

Show all of your work to receive full credit.



1. The mummy of a hunter was found frozen on the Italian Alps. Carbon-14 dating methods found that the body contained 52.5% of the original carbon-14 that would have been in his body at his time of death. Determine the age of the ice mummy. 52.5% carbon-14 = 0.8 half lives 0.8 half-lives x 5.73x103 = 4584.0 years 2. Use the following diagrams to complete the next short answer question (on the following page)



a) The seismograms show two waves arriving at each seismic station. Identify which type of seismic wave is the first to arrive at each station and which type of seismic wave is the second to arrive. Justify your answer. (2 marks) P waves travel the fastest followed by the S waves. Pwaves are fastest.

b) Determine the distance from the epicentre to each seismic station by using the seismogram for each station and the S-P graph. (3 marks) Station #1: Station #2: Station #3:

c) It is possible to rank the distance of each seismic station to the epicentre from closest to farthest. Explain which feature on each of the seismograms confirms the order and how it is used to determine the relative distance from the epicentre to the seismic station. (2 marks)

d) Use the nomogram to determine the Richter magnitude of this earthquake. Show all of your work, including the values you used. (1 mark)

unit c: key the changing earth - ms. mogck's classroom€¦ · unit c: key the changing earth...

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