the effect of the moon on tides - telecom...
TRANSCRIPT
Name:_____________________________________________________
Read each article. Then, create the following thinking maps to go with the articles:
Article 1: Ocean Tides
Create a DOUBLE BUBBLE MAP that compares and contrasts the effect of the sun on tides and the effect of the moon on tides. (ADD BUBBLES AS
NEEDED)
Tree Map: Create a TREE MAP that classifies the four different types of tides. Be sure to DESCRIBE each tide briefly underneath. The first one is done
as an example.
The effect of the sun on tides
The effect of the
moon on tides
Types of Tides
Spring Tide
Higher than normal
high tide, affected by
the sun-during new
moon or full moon
Article 2: The Ocean Conveyor Belt
Currents
CURRENTS
TYPES OF CURRENTS
CAUSES OF CURRENTS
IMPORTANCE OF CURRENTS
EXAMPLES OF CURRENTS
Create a CIRCLE MAP that defines what currents are, using infor-
mation from the article.
Fill in the TREE MAP with information from the article to support/describe/elaborate on each branch
First,
Create a FLOW MAP that details the steps of how an ocean freezes.
Next,
Then,
Finally,
Name:_____________________________________________________
Read each article. Then, create the following thinking maps to go with the articles:
Article 3: “The Big One” by sea and not by land
Create a DOUBLE BUBBLE MAP that compares and contrasts the San Andreas Fault with the Cascadia Fault. ADD BUBBLES TO THE MAP.
Tree Map: Create a TREE MAP that explains why the Cascadia
Fault is dangerous. USE INFORMATION FROM ARTICLE.
San
Andreas
Fault
Cascadia
Fault
Reasons why Cascadia Fault is Dangerous
Create a BUBBLE MAP describing
Tsunamis. ADJECTIVES ONLY. Each
bubble should have ONE word, a
“describing word” (Example given)
Tsunamis
BIG
Article 4: Ridges and Trenches
Create a DOUBLE BUBBLE MAP that compares and contrasts RIDGES and TRENCHES. (ADD BUBBLES AS NEEDED)
Tree Map: Create a TREE MAP that classifies the four different types of tides. Be sure to DESCRIBE each tide briefly underneath. The first one is done
as an example.
RIDGES TRENCHES
Evidence of How Mid-Ocean Ridges Form
1
Ocean Tides
6E3BD Atmosphere, Water Cycle, Waves, and Currents
Earth and Space
1 The gritty sand oozes between your toes as you
stroll along the beach. The gentle lapping of the
waves lulls you into a peaceful state. The ocean
water appears to stretch its cool fingers farther up
onto the shore than it did earlier in the day. Is it
your imagination or is the water level rising?
2 Well, you may feel better knowing that it is not your
mind playing tricks on you. Throughout each day,
the ocean water rises and falls at different times.
This movement of water is known as a tide. A tide
is a change in water level at the shoreline; it is being caused by the pull of gravity between
Earth and the Moon and Earth and the Sun. During each 24-hour period, the beach will
experience two high tides and two low tides in most places around the world. Periodically,
the beach will also experience a spring tide and a neap tide.
3 How does the gravity between the Moon and Earth cause a tide? Each day, the beach can
expect a high tide, a low tide, another high tide, and then another low tide. Between each of
these tides is approximately six hours. This is important to know because each quarter turn
of Earth takes six hours. Earth will make four quarter turns in a 24-hour period. With each
turn, the Earth and the Moon will be in different positions. These positions determine if it is a
high or low tide. These tides are a direct effect of the Moon's gravity tugging on the water on
Earth.
4 The Moon's gravity has a powerful effect on Earth's waters. In fact, it is far more powerful
than the Sun's effect. Why, you ask? It is because the Moon is closer to Earth than the Sun.
The Moon pulls the water that is on the side of Earth facing the Moon toward itself in a big
bulge. At the exact same time, on the side of Earth that is facing away from the Moon,
another bulge is forming. These two places will experience high tides. The opposite places
on Earth, which are not facing toward or away from the Moon, will experience low tides. As
Earth keeps making quarter turns, the tides change from high to low and low to high.
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6E3BD Atmosphere, Water Cycle, Waves, and Currents
Earth and Space
5 How does the Sun affect the ocean tides? As mentioned before, the Sun has less of an
effect on the tides. However, the gravitational tug of the Sun can increase a high tide by
making it rise higher than normal. This is known as a spring tide. A spring tide has
absolutely nothing to do with the season spring. A spring tide happens when the Moon is
either in its new moon or full moon phase. The Moon, Sun, and Earth line up perfectly with
one another. This allows their gravitational pull on the ocean to work together making the
high tide rise higher.
6 A neap tide is the opposite of a spring tide. A neap tide is a lower than normal high tide. At
the same time, there is also a higher than normal low tide. This happens as the Moon
enters a first and last quarter moon phase. At this time, the Sun and the Moon are in
positions that form a right angle to one another. The gravitational pull of the Sun pulls
water away from the bulge formed by the Moon at high tide. The water moves toward the
places that are having low tides. This results in a low high tide and a high low tide.
7 In a 24-hour period, a beach will have two high tides and two low tides. When the Moon is
new or full, it will line up with the Sun and Earth causing a spring tide. When the Moon and
the Sun form a right angle to one another, there will be a neap tide. The next time you visit
a beach, pay attention to the water level on the shoreline. You might just experience a high
or low tide yourself. As you do, remember that the gravitational pull of the Moon is what is
causing the ocean tides.
3
1 Which statement best describes what an ocean tide is?
A A change in water level that makes a high tide higher
B A change in water level at the shoreline that is being caused by the
gravitational pull of the Moon
C A change in water level at the shoreline that is being caused by the
gravitational pull of the Sun
D A change in water level that makes a low tide lower
2 What effect does the Sun have on the ocean tides?
A The Sun does not have an effect on the ocean tides because it is too far
away.
B The Sun warms the water causing it to rise.
C The gravitational pull of the Sun causes spring and neap tides.
D The gravitational pull of the Sun's gravity is more powerful than the Moon's.
6E3BD Atmosphere, Water Cycle, Waves, and Currents
Earth and Space
4
3 During a spring tide, the Moon is either in its new moon or full moon phase. What
effect does this have on an ocean tide?
A The Moon, Sun, and Earth line up perfectly with one another, allowing their
gravitational pulls to work together and making the high tide rise higher.
B The Moon and Sun are positioned at a right angle to one another causing a
lower than normal high tide. The Sun warms the water causing it to rise.
C In most places, the beach will experience two high tides and two low tides.
D A spring tide only happens during the springtime.
4 How does the gravity between the Moon and Earth cause the tides to rise and
fall?
A The position of the Sun interferes with the Moon's gravity.
B During each quarter turn that Earth makes, the Moon and Earth line up in
different positions allowing for the high and low tides.
C Earth makes four quarter turns each day causing spring and neap tides.
D The gravity of the Moon is stronger at night than during the day.
6E3BD Atmosphere, Water Cycle, Waves, and Currents
Earth and Space
5
5 What is the main point of paragraph 3?
A Solar flares affect the tides.
B Tides are not affected by the Moon's orbit.
C The neap tide is the opposite of the spring tide.
D Gravity between the Moon and Earth causes different tide levels.
6E3BD Atmosphere, Water Cycle, Waves, and Currents
Earth and Space
The Ocean Conveyor Belt
1 Water in the ocean is always
moving. Waves break the surface.
Currents move in the shallows and
in the depths. Currents near the
surface are mainly caused by the
winds and tides. Deep water
currents run on a different engine.
2 Currents run through all of the
Earth’s oceans. They are important
for several reasons. The currents
help keep global temperatures even. They move energy around the oceans. Otherwise, the
3 Currents also cycle nutrients through the ocean. Water near the surface is rich in oxygen.
Deep waters are rich in nutrients. When sea creatures die, they sink to the ocean bed. They
decay and release nutrients into the deep water. There must be a way to mix and exchange
the two. In fact, there is—a slow global deep water current. Wallace Broecker is a noted
oceanographer. Broecker named this the ocean conveyor belt.
4 Deep ocean currents are caused by thermohaline circulation. What does this mean? Well,
“thermo-” means temperature. And “-haline” means salt. But how do temperature and salt
cause currents? The linking factor is density.
5 Density is a physical property of all materials. It is the measure of how much mass the
material has for a standard particular volume, generally 1 cm3. Whether something sinks or
floats on a liquid is based on its density. A more dense substance, either liquid or solid, will
sink to the bottom. A less dense substance will be found on the top. Water is more dense as
a liquid than as a solid. This is why ice floats. Liquid water can vary in density. As long as it
remains a liquid, water gets more dense as it gets colder. Also, water’s properties change
based on how much salt is dissolved in it. The measure of salt in a water sample is called
salinity. Water gets more dense as its salinity goes up.
6E3A Earth’s Water
Earth and Space
1
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equator and tropics would get too hot. The poles would get too cold. While deep water
currents do play a part in energy transfer, this is mainly done by surface currents. These are
currents in the top 100 meters of the ocean. Their main driving force is the wind. They flow
quickly and form giant circles. One example is the Antarctic Circumpolar Current, which
forms a giant ring around the continent of Antarctica.
6 There are three special places on Earth where conditions are right to pump the ocean
conveyor belt. Two are in the North Atlantic Ocean. The other is the Weddell Sea off the
coast of Antarctica. All three locations lie near either the north or south Arctic Circle. On the
map at the top of this passage, these locations are labeled “deep water formation.”
Conditions are right in these places to make water very, very dense. It will sink to the bottom
of the ocean. But how does this happen? We will focus on the Weddell Sea for the answer.
Remember that a similar process happens in the North Atlantic to form deep water.
7 During the winter months, air temperatures in Antarctica are very cold. Areas surrounding
Antarctica get very little sunlight for much of the winter. Moving closer to the South Pole,
some areas get no sunlight at all for weeks. Very cold winds from the interior of the Antarctic
continent blow away from the South Pole. At the Weddell Sea, local geography funnels
these winds over the surface of the water. The Weddell Sea is fringed year round by ice
sheets. Conditions are much colder in the winter. Sheets of ice form rapidly. Much of the sea
has seasonal ice coverage. This rapid ice formation is one piece of the puzzle. The strong
icy winds are another.
8 When ice forms from salt water, an interesting thing happens. The ice that forms is pure
water. The salt gets left behind. (This works as long as some of the water remains liquid.) In
the Weddell Sea, there is rapid formation of lots of pack ice. Much of the salt is left behind.
This leads to water with very high salinity. There is another interesting property of water. As
the salinity of a water sample goes up, its freezing point goes down. This means that very
salty water will stay liquid below the freezing point of fresh water. The icy winds cool the
water, often to -1°C (30°F). The winds turn this high salinity water into the coldest,
densest water in Earth’s oceans. It sinks. This forms the Antarctic Bottom Water. The other
two locations form slightly less dense North Atlantic Deep Water.
9 The sinking of the newly formed deep water pushes the water from previous years. This
drives the slowly moving ocean conveyor belt. The Antarctic Bottom Water forms a current
that travels around the continent of Antarctica. The North Atlantic Deep Water slowly creeps
south to join these currents. Portions of the giant current break off. They travel along the
bottom of the Indian and the Pacific Oceans. The deep currents are shown in blue in the
image at the top of this passage. Finally, they will return to the surface. These upwellings
bring nutrients up to replenish surface water. Scientists think deep water may take between
600 and 1,000 years to return to the surface.
6E3A Earth’s Water
Earth and Space
2
1 What is the driving force of the deep water ocean conveyor belt?
A Winds push the deep water into the Pacific and Indian Oceans.
B Gravity from the Moon pulls the deep water toward the equator.
C The spinning of the Earth makes the deep water current run in circular
paths.
D Very cold temperatures create very dense water that pushes the deep
current along.
2 What is the meaning of circumpolar in paragraph 2?
A Circular path around the pole
B Wind-blown current
C Cold and salty
D Sinking
6E3A Earth’s Water
Earth and Space
3
4 Which location on the map above is a source of North Atlantic Deep Water?
A A
B B
C C
D D
Examine the map below. Use it to answer questions 3 and 4.
6E3A Earth’s Water
Earth and Space
4
3 Based on the information in the passage, which location on the map above marks
the Weddell Sea?
A A
B B
C C
D D
B
A
D
C
5 Which of these characteristics will produce the most dense water?
A High salinity, high temperature
B High salinity, low temperature
C Low salinity, high temperature
D Low salinity, low temperature
6E3A Earth’s Water
Earth and Space
5
"The Big One" by sea and not by land
Surfer Lee Johnson emerges from the water at San Onofre State Beach, Calif., with the twin domes from the San Onofre
Nuclear Generating Station in the distance. Officials have said the plant can sustain a 7.0 quake but not the 9.0 that
struck Japan in 2011. Photo: Mark Boster/Los Angeles Times/MCT
LOS ANGELES — Scientists worry that a strong earthquake off the coast of California
could do major damage to the West Coast.
Earthquakes on land can cause a lot of damage. But earthquakes in the ocean have their
own dangers. These earthquakes can cause a tsunami, a huge wave that rushes into
coastal cities.
The Cascadia fault line, 700 miles off the coast of Northern California, could produce a
tsunami that would heavily damage the West Coast, scientists say.
A giant tsunami along the West Coast would wash away towns, destroy U.S. Highway 101
and cause $70 billion in damage. The wave could destroy bridges, knock down power
lines, and cut communication systems like phones or Internet.
It’s possible that people would only have 15 minutes to escape. As many as 10,000 people
could die.
By Los Angeles Times, adapted by Newsela staff on 03.24.14
Word Count 629
Early Warning System
Officials in California, Oregon and Washington are now making plans to prepare for an
earthquake and tsunami. They hope to learn lessons from a 2011 disaster in Japan. A 9.0
earthquake there created a huge tsunami that flooded coastal areas.
That tsunami took people by surprise. It killed more than 10,000 and left more than
300,000 homeless. It also damaged a nuclear power plant. A meltdown at the plant spread
dangerous radiation in the area.
Researchers on the West Coast hope to save lives by quickly spotting a tsunami and
warning local citizens. They hope that new tsunami detectors deep under the ocean can
provide early warnings.
Predicting a tsunami’s strength is important to saving lives. Japanese scientists did not
realize how big their tsunami was. Local people were not prepared, and many lost their
lives.
It’s very important to have correct information, said Vasily Titov, head of the U.S. National
Oceanic and Atmospheric Administration's (NOAA) Center for Tsunami Research.
Escape To High Ground
To escape a tsunami, people must get to high ground such as a hill or mountain. But in flat
areas, there is nowhere to go. Safety officials must build high ground.
One idea is buildings with roofs that can protect people from a tsunami. One of these at a
school in Washington will protect 1,000 people with a high wall.
Officials have also discussed building man-made hills. Each hill could hold as many as
800 people.
California is famous for the San Andreas fault. This fault runs through the heart of the state.
It produced the famously scary 1906 San Francisco earthquake. The 1906 quake killed
more than 3,000 people.
Scientists now think that the Cascadia fault is more dangerous than they thought.
The Cascadia fault is made up of three tectonic plates that are pushing against each other.
The most powerful earthquakes in the last 10 years in California were caused by Cascadia.
Scientists had believed that the Cascadia fault could only produce a 7.5 earthquake. But
they now believe that it could create an enormous 9.0 quake.
Like A Rubber Band
The Cascadia fault is dangerous for two reasons. First, it is very long.
Second, it is an area where two huge tectonic plates are being pushed under the even-
larger North American plate. The smaller plates push under little by little, dragging the
North American plate down with them.
But the North American plate is old and strong, and it won’t be pulled down forever.
Once every couple hundred years, the North American plate snaps back upward like a
rubber band, creating a strong earthquake.
On March 16, a small earthquake caused by the Cascadia fault erupted 50 miles off the
coast, causing light shaking. No injuries or damages were reported.
The West Coast was spared this time, but scientists still wonder when “The Big One” will
hit.
“It could be today. It could be 100 years from now,” U.S. Geological Survey seismologist
David Oppenheimer said.
Quiz
1 What are two MAIN ideas of the article? Fill in the blank.
Scientists are worried that a strong tsunami on the __ fault line will cause a serious tsunami; we
can prepare by _.
(A) Cascadia; setting up tsunami warning systems and and building on high
ground.
(B) San Andreas; moving people to different cities that are safer and less prone
to earthquakes.
(C) Japanese; setting up sensors underwater to detect earthquakes and
tsunamis.
(D) Oregon; fundraising to pay for protective barriers and also to pay for
rebuilding destroyed areas.
2 Which of the following accurately summarizes the section "Like A Rubber Band"?
(A) The San Andreas fault is like a rubber band because the North American
plate gets pushed down and snaps back up every couple hundred years.
(B) The Cascadia fault is like a rubber band because the North American plate
gets pushed down and snaps back up every couple hundred years.
(C) The Cascadia fault is like a rubber band because there are a bunch of
tectonic plates knocking into one another constantly like bumper cars.
(D) The Cascadia fault is like a rubber band because it always produces the
world's largest earthquakes every 1,000 years.
3 According to the article, what is the relationship between earthquakes and tsunamis?
(A) Tsunamis typically occur in costal areas, and earthquakes occur in land-
filled areas.
(B) Earthquakes only occur in where there are mountains, and tsunamis occur
where warm water and air mix.
(C) An earthquake that occurs in the ocean may cause a huge wave, called a
tsunami, that can destroy coastal cities.
(D) An earthquake that occurs on land may cause a huge tsunami that can
destroy marine life far away from the shore.
4 Why are officials in California, Oregon and Washington interested in a 2011 disaster in Japan?
(A) The Japanese experienced a tsunami caused by an earthquake, which is
precisely what the West Coast is preparing for.
(B) Researchers on the West Coast hope to avoid what happened to the
Japanese by installing tsunami detectors.
(C) Both option A and B.
(D) Natural disasters that happen in Japan are always used by scientists to
predict natural disasters in other countries.
Answer Key
1 What are two MAIN ideas of the article? Fill in the blank.
Scientists are worried that a strong tsunami on the __ fault line will cause a serious tsunami; we
can prepare by _.
(A) Cascadia; setting up tsunami warning systems and and building on
high ground.
(B) San Andreas; moving people to different cities that are safer and less prone
to earthquakes.
(C) Japanese; setting up sensors underwater to detect earthquakes and
tsunamis.
(D) Oregon; fundraising to pay for protective barriers and also to pay for
rebuilding destroyed areas.
2 Which of the following accurately summarizes the section "Like A Rubber Band"?
(A) The San Andreas fault is like a rubber band because the North American
plate gets pushed down and snaps back up every couple hundred years.
(B) The Cascadia fault is like a rubber band because the North American
plate gets pushed down and snaps back up every couple hundred
years.
(C) The Cascadia fault is like a rubber band because there are a bunch of
tectonic plates knocking into one another constantly like bumper cars.
(D) The Cascadia fault is like a rubber band because it always produces the
world's largest earthquakes every 1,000 years.
3 According to the article, what is the relationship between earthquakes and tsunamis?
(A) Tsunamis typically occur in costal areas, and earthquakes occur in land-
filled areas.
(B) Earthquakes only occur in where there are mountains, and tsunamis occur
where warm water and air mix.
(C) An earthquake that occurs in the ocean may cause a huge wave, called
a tsunami, that can destroy coastal cities.
(D) An earthquake that occurs on land may cause a huge tsunami that can
destroy marine life far away from the shore.
4 Why are officials in California, Oregon and Washington interested in a 2011 disaster in Japan?
(A) The Japanese experienced a tsunami caused by an earthquake, which is
precisely what the West Coast is preparing for.
(B) Researchers on the West Coast hope to avoid what happened to the
Japanese by installing tsunami detectors.
(C) Both option A and B.
(D) Natural disasters that happen in Japan are always used by scientists to
predict natural disasters in other countries.
Ridges and Trenches
1 More than 100 years ago, geologist Alfred
Wegener made an interesting connection.
Wegener realized that the coastlines of
America and Africa fit together like a jigsaw
puzzle. Also, similar fossils are found on both
continents. He proposed that the continents
had once been joined. They had later drifted
apart. He did not know how this continental
drift happened. New technology was required
to discover the underwater ridges and
trenches that make continental drift possible.
2 Most scientific discoveries combine observation and inspiration. In the 1950s, Marie Tharp
and Bruce Heezen led a team of geologists. They made the first scientific map of the ocean
floor. They sailed around the ocean. They made many measurements of water depths. They
found a vast mountain range running along the middle of the Atlantic Ocean. They named it
the Mid-Atlantic Ridge. At first they thought that this ridge was unique to the Atlantic Ocean.
Later they found that ridges are in most oceans. These scientists discovered that mid-ocean
ridges existed. They still did not know how they formed.
3 Later studies by other scientists provided clues to how mid-ocean ridges form. Geologists
measured the magnetic properties of the ocean floor near the ridges. They found a pattern
of “stripes.” Rocks record the magnetic orientation of Earth at the time they are formed.
Earth’s magnetic field flips orientation every few million years. Therefore, the stripes
alternate. Importantly, the stripes are the same on both sides of the ridge. This suggests that
rock moves away from the ridge in both directions. Geologists found the age of rocks at
different distances from the ridge. Their data showed that younger rock is closer to the ridge.
Older rocks are found farther from the ridge. The last piece of evidence is from pictures of
ridges. The ridges show lava flows like those seen on volcanoes on land. These
observations led scientists to propose that seafloor spreading is part of continental drift. This
is also known as plate tectonics. The theory of plate tectonics explains how Earth looked in
the distant past. It explains many modern features. Plate tectonics allows us to predict how
Earth might look in the distant future.
4 We now know that the seafloor itself moves. It carries the continents with it. The entire crust
of Earth is divided into about 15 plates. These plates move on top of a semisolid mantle.
The movements are powered by convection currents. New crust forms at the mid-
1
6E3C Ocean Topography
Earth and Space
Lexile 760L
ocean ridges. It moves away from the ridges in both directions. The plates are moving away
from each other. Therefore, these areas are called divergent plate boundaries. Between 2
cm and 20 cm of new crust are formed at each mid-ocean ridge. A fissure in Earth’s crust
allows magma to erupt; it then cools into new crust. Eruptions and small earthquakes are
common along the 65,000 km of mid-ocean ridges encircling Earth. The formation of new
crust increases the distance between continents. It makes some oceans bigger.
5 New crust is being added continually at mid-ocean ridges. Doesn’t that mean that Earth is
always getting bigger? If addition of new crust were the only process at work, the answer
would be yes. Some scientists do think Earth is actually getting bigger. However, most
scientists think Earth stays pretty much the same size. To keep Earth at the same size, crust
must be destroyed at about the same rate as it is created. In fact, old crust is destroyed at
convergent boundaries. Old crust goes back into the mantle through the process of
subduction. How does this work? Continents are carried along the moving plates. Some
plates collide and break apart. These movements cause earthquakes and volcanic activity.
6 Here is where ocean trenches become important. Ocean trenches are also called submarine
valleys. They are the deepest parts of the ocean. Scientists must use special submarines to
explore the trenches. The water pressure is very high at these extreme depths. The
pressure can be equal to a car sitting on top of one square centimeter. The Marianas Trench
in the western Pacific Ocean reaches depths up to 11 km. Mount Everest is the tallest
mountain on Earth. Mount Everest could fit into the trench with 2 km to spare! These
trenches form where two tectonic plates come together. This is usually a continental plate
and an oceanic plate. The oceanic plate is denser. It gets pushed under the continental
plate. The oceanic plate goes back into the mantle and melts. This process often creates
earthquakes or hot spots that cause volcanoes. A perfect example of this is an area known
as the Pacific Ring of Fire. This large area forms a horseshoe shape around the Pacific
Ocean. It runs along the eastern coasts of Indonesia and Japan, north to Russia. Then it
extends to the west coast of North America, all the way to South America. It has the largest
number of active volcanoes and destructive earthquakes on the planet. Most of this activity
is due to subduction of the seafloor under tectonic plates at the continents’ edges.
7 The basics of the theory have been worked out over the last century. Research is still
discovering new aspects. Two large earthquakes were recorded in the Indian Ocean in
2012. These earthquakes suggest that the Australian and Indian plates are separating. The
actual separation will probably take several million years. Large earthquakes, however,
might become more common. Geologists have studied earthquake waves passing through
the crust near the California coast. Data show that a chunk of an ocean plate is still stuck to
the bottom of the continental plate. Subduction may therefore not always be smooth.
Research also shows that Earth may not be the only planet with plate tectonics. A large
canyon system on Mars seems to have fault lines. Fault lines often mark plate boundaries.
Several long lines of volcanoes suggest that a tectonic plate moved slowly over a hot spot.
6E3C Ocean Topography
Earth and Space
2
2 Which of the following correctly defines a divergent boundary?
A A small part of Earth’s mantle
B A location of high volcanic activity
C A location where tectonic plates move apart
D A section of crust that moves as a unit
1 Which of the following pieces of evidence does not explain how mid-ocean ridges are
formed?
A The rocks closer to the ridge are younger than those farther away.
B Mid-ocean ridges are found on the bottom of most oceans.
C The magnetic orientation of rocks is symmetrical on either side of mid-ocean
ridges.
D Pictures of ridges show evidence of lava flows.
6E3C Ocean Topography
Earth and Space
3
3 Which of the following is LEAST NECESSARY for plate tectonics?
A A solid core inside the planet.
B A semisolid mantle.
C Convection currents in the mantle.
D A crust divided into plates.
4 Which of the following statements regarding a convergent plate boundary between
continental crust and oceanic crust is not true?
A Earthquakes are common at the boundary.
B Mountains are formed.
C Hot spots that may create volcanoes are formed.
D Oceanic crust changes into continents.
6E3C Ocean Topography
Earth and Space
4
5 Subduction of ocean crust happens–
A at a mid-oceanic ridge.
B far from tectonic plate boundaries.
C inside volcanoes of the Ring of Fire.
D in deep ocean trenches.
6 What evidence suggests that the Australian and Indian plates are separating?
A The formation of a new oceanic ridge
B Recent large magnitude earthquakes
C The way earthquake waves travel through the area
D The presence of a string of volcanoes
5
6E3C Ocean Topography
Earth and Space