Natural Disasters Exam 3
Terms in this set (85)
Why is it incorrect to refer to a tsunami as a "tidal wave"?
A tsunami has nothing to do with the tides
Know the primary characteristics of a tsunami
-Tsunami have extremely large wavelengths (> 500 miles), very long periods
(10-60 minutes), low wave height (< 1 m), low steepness (never a breaking wave)
and very high speeds (450 mph).
-Tsunami can pass unnoticed beneath ships at sea.
-When the tsunami wave enters shallower water near a coast, it slows down
and its wavelength shortens, causing a strong buildup of its height and water
What is a visual sign of an
The sea recedes from the coast,
exposing the sea floor.
If drowning does not kill people in the way of a tsunami, what does?
The huge amount of floating debris (trees, pieces of buildings, autos, etc.) in
the flood waters.
What are the four primary causes of
1) earthquakes; 2) volcanoes; 3) landslides
(on land and under water); and, 4) space
impacts (high velocity asteroids and comets).
What is the minimum Mw value for an
EQ to trigger a tsunami?
Is it possible to know which tsunami wave will be the largest?
No, it is not possible.
the largest EQ ever recorded at 9.5 Mw created a tsunami that killed over 1000 people in Chile and then crossed the entire Pacific Ocean, killing 61 people in Hawaii (14 hours later) and killing 282 people in Japan (22 hours later).
the second largest EQ ever recorded at 9.2 Mw created
a tsunami that killed 125 in Alaska and then another 12 people in Crescent City, California, when the 5th wave was the largest.
Indian Ocean 2004
a 9.1 Mw EQ send a tsunami all across the Indian
Ocean, causing death and destruction in 13 countries, killing 245,000 people
a 9.0 Mw EQ sent a tsunami (20-133 feet high) into Japan, killing over 19,000 people.
What could have saved countless lives in the Indian Ocean tsunami
Education and a warning system.
the collapse of the volcano during its eruption sent several tsunami into the islands of Sumatra and Java, destroying 165 villages and killing 36,000 people.
Lituya Bay, Alaska 1958:
an 8.0 Mw EQ triggered a massive landslide into the Lituya Bay, creating the largest tsunami wave run-up
on record (110 feet above sea level), as marked by the trees that were stripped off the surrounding mountains along the bay.
Which Atlantic Ocean island chain is a potential tsunami threat to
Canary Islands (Cumbre Vieja volcano on La Palma)
What creates the largest, but rarest, tsunami?
The impact of high-velocity asteroids and comets.
Know the basic personal tsunami safety actions.
○Abandon personal belongings and run for
○ Climb to an upper floor or roof of a strong
○ If no higher ground or tall, strong
buildings, then climb a tree.
○ Last resort if no trees, grab onto
something that floats to use as a raft.
Why are there so few impact craters visible on Earth?
The craters are "erased" through plate tectonics (consumed at subduction zones; crumpled in continent-continent collisions) and by erosion.
pieces of asteroids and comets that orbit the sun
when a meteoroid blazes through Earth's atmosphere, it is referred to as a meteor or "shooting star."
a meteor that reaches the Earth's surface
What are asteroids and where are they located?
The asteroids are rocky, metallic and icy masses and lie between the inner and outer planets (between the orbits of Mars & Jupiter)
What is the composition of comets? Why does its "tail" point away from the Sun?
○ Comets are "dirty snowballs" made of
ice and rocky debris.
○ As a comet approaches the sun, the solar
wind sublimates the outer portion of the
comet, creating a luminous tail that always
points away from the sun.
Why are comets thought to have possibly brought "life" to Earth?
The ices of comets contain carbon compounds known to be the building
blocks of life. Comets may also carry bacteria known as extremophiles
About how many meteoroids enter Earth's atmosphere every 24 hours?
An estimated 100,000 million or more meteoroids enter Earth's atmosphere every 24 hours!
What two factors determine the amount of energy released in an impact?
The energy released by an impact depends on its speed and mass
Be able to visually distinguish between a small impact crater from a large one.
○ The impact of small meteorites creates
simple craters, with raised rims and concave
bottoms, lacking central uplifts (such as Meteor
Crater near Winslow, AZ)
○ The impact of larger bodies form complex craters,
with central uplifts and collapsed outer rims.
What new minerals are created during a large body impact?
The extremely high temperatures and pressures in a large body impact break, melt and vaporize the rocks in the crater, creating hexagonal nano-diamonds and can transform quartz into stishovite (shocked quartz)
†What comet impacted Jupiter during 16-22 July 1994?
How many impact craters are there worldwide? In the U.S. and Canada?
There are 164 known impact craters, including 56 in the U.S. and Canada
Know the effects of a large asteroid impact on land and in the oceans.
○ Impact on land: Besides creating powerful earthquakes (MW > 11), there would be worldwide wildfires, acid rain (due to nitrogen oxides in the
atmosphere), along with lots of dust and soot to block sunlight making photosynthesis difficult for weeks to several months. In the longer term, global warming would occur due to increased water vapor and CO2 left in the atmosphere.
○ Impact in an ocean: Besides creating powerful earthquakes and huge tsunami, it would create a bubble of steam that would carry Earth rock and
asteroid debris into the atmosphere and if it reaches the ocean floor could release tons of CO2 from the limestone sediment. In the longer term, it would create an extra cold "winter," followed by an overly hot and long "summer!
What are NEOs? What is the "Torino Scale"?
○ NEO stands for "Near Earth Object" and about 90% of the NEOs are asteroids or short-period comets.
○ The "Torino Scale" is a scale from 0 (no collision hazard) to 10 (global catastrophe) that assess the threat of a single comet or asteroid impact.
What are the possible mitigation strategies for a potential impact?
○ There are no formal plans at this time!
○ Some possible mitigation strategies include
blowing it apart with an nuclear explosion, attaching
a rocket engine to drive it away, use a big mirror to
focus sunlight to vaporize it, scooping rock out of it to
toss it away, and to launch a heavy "space tractor" to
use gravity to pull it away from a Earth-collision path.
What is the significance of Asteroid 99942, also known as "Apophis"?
○ This asteroid made a close pass to Earth in 2012, but on Friday, 13 April 2029, it will pass only 18,000 miles above the mid-Atlantic Ocean. After that near-miss, if Earth's gravity gives it a good pull, it could return and impact Earth on Easter Sunday, 13 April 2036!
What was the biggest impact event of the 20th Century?
Tunguska, Siberia, 1908: a massive fireball (icy comet or stony meteorite) exploded above the ground.
Was the Barringer Crater in AZ created by a large or small impact?
Small impact, because the crater has a raised rim, a concave bottom and is lacking a central uplift.
What led Luis Alvarez to propose that an asteroid impact killed the dinosaurs?
He found an abnormally high percentage of the element iridium in a clay layer near Gubbio, Italy, dating back to the K/T boundary time period. (Iridium is only found deep in the Earth in the iron-rich core, but meteorites are enriched in iridium.)
How and where did they eventually locate the crater from the K/T impact?
The Mexican national petroleum company (PEMEX) was drilling for oil in the Yucatan Peninsula and encountered a 90 m (300 ft) thick zone of shattered rock containing shocked quartz and glassy blobs of once melted rock. Geological surveys revealed that the Chicxzulub crater was caused by an estimated 10km (>6mi) wide asteroid that dated back 65 million years ago!
†Statistically, are you more likely to be killed by a tornado or by an asteroid with a diameter of 1 km or greater in the next 50 years?
Tornado (1 in 60,000)
The presence of free hydrogen and a lack of oxygen
rich in nitrogen & oxygen, and deficient in CO2
What are fossils and why are there none older than ~543 million years ago?
Fossils: are evidence of former life, that had
"hard parts" and a rapid burial. Life prior to 543
million years ago did not have "hard parts" to become fossilized
What percentage of all plant and animal
species that have ever lived are extinct?
the smallest biologically real and distinct unit of individuals that share a common ancestor not shared with other organisms.
a worldwide elimination of numerous species (40% or
What are the archaea and when did they live?
Archaea (extremophiles) were alive 3.8 billion years ago; they were an ancient branch of life that thrived under high pressures and high temperatures; they derived their energy by breaking chemical bonds of inorganic molecules (CO2, H2O, N2)
What are stromatolites and what life form made them?
Stromatolites are layered structures under shallow
water that were made by cyanobacteria (photosynthetic bacteria)from 3.5 to 2.5 billion years ago.
When did our distant ancestor (eukaryotes) arrive on the scene?
About 2.1 billion years ago, after a "Snowball Earth" episode
What did the arrival of sexual reproduction have on evolution about 1 billion years ago?
Sexual reproduction allowed cells to share and mix genetic material, thus speeding up evolutionary changes by thousands of times.
What caused the "Cryogenian Period" 750 to 620 million years ago?
After the breakup of the supercontinent Rodinia,
most of the continents were near the equator. The barren land was highly reflective, which caused global cooling and the huge abundance of cyanobacteria in the oceans led to a significant decrease in CO2
and an increase of O2, which further enhanced global
cooling. This led to as many as four "Snowball Earth" episodes and is called the "Cryogenian Period."
When was the "Cambrian Explosion" and what happened prior?
Following the Cryogenian Period about 620 million years ago, a very warm period saw an explosion of cyanobacteria that put so much oxygen into the atmosphere that the ozone layer began to form. Soon after, multicellular sea life appeared. Then, about 543 million years ago, there was a 40 million year burst of remarkable evolutionary change known as the "Cambrian Explosion."
What allowed the fishes to leave and oceans, to become land dwellers?
The formation of a full ozone layer (about 400 million years ago) blocked harmful UV radiation from reaching Earth's surface. This allowed life to leave
the oceans and vascular plant life appeared on land for the first time.
What was significant about the "Carboniferous Period"?
About 300 million years ago, oxygen levels may have risen as high as 35%. On land, there were Amphibians (as big as pigs), early reptilians (bigger than sheep) and HUGE INSECTS (millipedes as big as dogs, 50-pound scorpions, and dragonflies with 2- foot
wingspans). It was also a time of massive wildfires. This period led to much of the coal, oil and gas we are mining and using for energy today!
What role did the "Siberian Traps" and "Deccan Traps" flood basalts play?
○ The Siberian Traps Flood Basalt may have been the primary cause of the End Permian Extinction, in which 95% of all living marine species and 70% of all terrestrial vertebrate species died.
○ The Deccan Traps Flood Basalt in India combined with an asteroid impact to kill off 70% of all species on
Earth, including the dinosaurs (except birds).
How long did the dinosaurs rule the planet?
For about 165 million years!
What life took over from the extinct dinosaurs?
Mammals took over the land vacated by the dinosaurs
What was the "Torrid Age?"
During the "Torrid Age" about million years ago, most of the tropical oceans were continent-free (low
reflectivity) and there was more heat in the oceans and atmosphere than at any time since
Has Earth been warming or cooling over the past 55 million years?
Over the past 55 million years, Earth has been cooling.
What likely began the more recent series of "Ice Ages"?
Volcanism had created the Isthmus of Panama, which
connected North and South America, thereby separating the Pacific and Atlantic Oceans and re- routing the ocean currents, thereby changing the
global circulation (bringing increased amounts of snow to higher latitudes). The Drake Passage at the
tip of South America opened up and isolated Antarctica. These two geologic events led to the formation of the polar ice caps.
10 possible causes of mass extinctions
1) Changes in sea floor spreading rates; high
spreading rates can lead to more rock in the oceans,
causing flooding and creating inland seas.
2) Sea level changes; the presence or lack of
glacial ice on the planet can give a total swing of 210 m (690 feet) total difference
3) Numbers and sizes of continents; combined
landmasses will have lesser diversity of species (due to competition for food supply and living space) than
smaller, isolated landmasses.
4) Continental position and glaciation; plays a
role in climate change and have led to the more recent
Ice Age episodes.
5) Volcanic causes; flood basalts have been directly linked to mass
extinctions; flood basalts in oceans will lead to a sea level rise.
6) Changes in atmospheric and oceanic composition; volcanic eruptions emit massive amounts of gases, including greenhouse gases, which cause changes in atmospheric gas concentrations; sub-sea eruptions can alter ocean water acidity and oxygen concentrations
7) Climate change causes; volcanic eruptions emit huge volumes of gases, altering the heat balance and affecting global climate.
8) Ocean composition causes; if the oceans become too warm, they can become anoxic (no oxygen); salinity changes (up or down) will affect species
9) Extraterrestrial causes; an asteroid or comet impact can cause a hard, dark "winter" that can last for weeks to months, followed by years to decades of
an overly hot "summer."
10) Biologic causes; species go extinct every day, as their numbers drop to dangerous levels ("gambler's ruin"); epidemic (pandemic) disease
To cause a worldwide mass extinction, what must occur?
Two or more causes described above must either occur simultaneously or be closely spaced in time on a global scale
443 million years ago; 3rd largest of the "Big
Five" and 2nd largest marine extinction; cause: continents gathering around the south pole, leading to significant global cooling, glaciation (Ice Age) and lowering sea levels.
364 million years ago; affected only marine life
(50% extinction); cause: sea level change, ocean anoxia, possibly triggered by global cooling and/or oceanic volcanism.
253 millions years ago; Earth's most severe mass extinction: ~95% of all marine species and 70% of all terrestrial species became extinct; it is also the only known mass extinction of insects; cause: combination
of events over different time scale: 1) Pangaea had formed, reducing lush tropical shorelines and creating a harsh interior; 2) sea floor spreading slowed, causing a fall in sea level; 3) Siberian Traps Flood Basalt put huge amounts of carbon dioxide (CO2) into the atmosphere, which led to significant global warming and a release of huge amounts of methane (CH4), leading to further global warming; 4) oxygen levels plunged, oceans became anoxic and released hydrogen sulfide (H2S), which poisoned the sea and the land, causing a Greenhouse Extinction!
What did the first two of the "Big Five" mass extinctions have in common?
They only affected marine life.
†Does doubling the size of a land mass allow for double the number of species?
A large, combined landmass will have a lesser number of species than several smaller, isolated landmasses.
Describe the "greenhouse extinction" process.
It begins with an abrupt and significant global warming caused by a sudden increase of atmospheric carbon dioxide (CO2), usually from flood basalt
eruptions. When the global warming reaches a 5* C increase, then methane (CH4) is released from the permafrost and frozen gas hydrates in the oceans,
leading to an additional 5* C global increase. The oceans become anoxic (devoid of oxygen) and sulfur bacteria release hydrogen sulfide (H2S), which poisons the oceans and then the land. As the poisonous H2S gas rises through the atmosphere, it destroys the ozone (O3) layer, killing any remaining life on land, including plant life.
#4) End Triassic
206 million years ago; Pangaea began breaking up;
50% of all species went extinct; oxygen was very low and CO2 high; cause: is unknown, but may have been caused by the "Central Atlantic Magmatic Province Flood Basalt (CAMP)" eruption, leading to another Greenhouse Extinction.
#5) End Cretaceous (K-T)
65 million years ago; 65% of all species went extinct,
including the dinosaurs (except birds); Pangaea
was in pieces, sea levels were falling, climates were cooling; cause: the Deccan Traps Flood Basalt in India was setting the state for another Greenhouse Extinction; this was capped by an asteroid impact in what today is the Yucatan Peninsula
What did the last three of the "Big Five" mass extinctions have in common?
They were all caused in part by flood basalt eruptions.
What is meant by "living fossils"? Give some examples.
○ Animals and insects that have been around for hundreds of millions of years and have survived several mass extinctions.
○ Horseshoe crabs, sharks, cockroaches
What (or who) has likely been responsible for the Quaternary extinctions?
Homo sapiens (us), the 6th Mass Extinction!
What is "The Last Extinction"?
many groups of large bodies animals went abruptly extinct about 12,900 years ago, near the end of the last "Ice Age"
†Where are the La Brea Tar Pits? What can be found there?
-downtown Los Angeles
-formed where oil from underground reservoirs seeped upward through fractures in overlying rocks to reach the surface
-the natural gas and lighter weight oils evaporated, leaving behind sticky, high viscosity asphalt in pools
- in the last 40,000 years, individual organisms representing more than 660 species have become stuck and entombed in the sticky asphalt
What is the current temperature trend over the past 30 years?
Earth is currently in a warming period.
What is up for debate in the current global warming?
The cause for the warming, the magnitude of the warming, and the proper solutions to mitigate the warming are still up for debate.
necessary for life on Earth because it helps to moderate Earth's temperature
is the term given to the Earth's warming in recent years as seen in global temperature trends.
What are the two types of global warming?
○ Natural Global Warming (GW) due to natural processes (solar energy absorbed, volcanic eruptions, sunspots, etc.)
○ Anthropogenic Global Warming (AGW): changes in the mean Earth temperature due to the influence of humans (burning fossil fuels, industrial pollution, etc.)
What is a "tipping point" in regards to world climate?
A "point" in which the climate has a catastrophic warming (or cooling) and quickly shifts to a completely different balance, one which would likely be far less hospitable to life.
What did the IPCC recently conclude?
That humans are playing a very significant role ( >90% certainty) in the modification of the worldwide climate
What is the best stance to take in regards to the global warming debate?
One should also treat all climate results with a dose of skepticism.
What are the two "best" human responses to global warming?
○ By cutting back on greenhouse gas emitting
methods and products, and shifting to non-polluting (green energy) fuels.
○ By geoengineering to help climate return to its "normal" stats, but there are risks and uncertainty in these methods.
†What likely led to the fall of the great Mayan civilization in Mexico?
- a centuries-long pattern of decreased rainfall caused problems that intensified during multi-year droughts, especially occurring between the years 800 to 1000CE.
- the droughts set off a chain of events that led the Mayans to permanently abandon many urban areas in the southern and central lowlands to stop construction of monuments, and to experience the breakdown of social and political order leading to wars.
- the advanced Mayan civilization declined significantly during a string of events triggered by long term climate change
†What gives the Stradivari violins their superior acoustical properties?
- the wood may be the reason for the superior acoustical properties of violins made during the late 1600s and early 1700s