Earthquake – Continental & Oceanic Plate – Earth Science
This earth-science lesson is about earthquake, oceanic and continental plate and their boundaries.
Where do most earthquakes occur?
Around the edge of the Pacific Ocean
An earthquake’s magnitude is a measure of the
Size of seismic waves it produces
What measurement for earthquakes do scientists use most often today?
Moment Magnitude Scale
Liquefaction occurs when
Loose, saturated soil turns into
liquid that can’t support buildings
A tsunami can occur when there is vertical movement at a fault under
The ocean floor
Earth’s thin, rocky outer layer is its
The Earth’s core is made of an alloy of
Iron and Nickel
What does Earth’s crust and uppermost mantle form?
Earth’s inner core is solid because of
The hypothesis of continental drift is used to explain an event that happened
Two hundred million years ago
What evidence supports Wegener’s hypothesis?
Fossils of the same organism have
been found on different continents
Which of the following results when divergence occurs within the oceanic
What forms when one oceanic plate is forced beneath another plate?
A subduction zone
Which of the following does NOT occur at a subduction zone?
a. The leading edges of both plates are
bent downward – correct
b. Oceanic crust is pushed down into the mantle
c. One oceanic plate moves into another oceanic plate
d. One continental plate moves into an oceanic plate
Which of the following is NOT evidence of seafloor spreading
a. the alternation of polarity in segments of the ocean floor
b. the relationship between earthquakes and plate boundaries
c. analysis of seafloor sediments
d. the distribution of ice sheets across
the planet – correct
Which of the following is true of a rock that has the property of
Rocks formed millions of years ago
show the location of the magnetic poles at the time of their formation
According to the theory of plate tectonics the ______ is divided into plates
What is the average movement of lithospheric plates?
5 cm per year
What kind of plate boundary occurs when two plates grind past each other
without destroying the lithosphere?
Transform fault boundary
A divergent boundary at two continental plates can result in a
What causes the thermal convection that drives plate motion?
Differences in temperature and
The geologic processes that shape Earth’s features today
Are basically the same today as they
were in the geologic past
In general, the law of superposition states tha tin an undeformed sequence
of sedimentary rocks, each layer is
Older than the one above it
According to the principle of cross-cutting relationships, an intrusive rock
Younger than the rocks it intrudes
Which type of geologic event has to occur to create and angular
Folding or tilting of rock layers
The laws of superposition and original horizontality are best applied to
What are fossils?
The remains or traces of an organism
preserved from the geologic past
Which of the following environments would NOT contain fossils?
a. sediment deposited in a riverbed
b. intrusive rock formed from cooled
c. a thick deposit of dried mud
d. layers of sand that accumulated over thousands of years
Which of the following is important if an organism is to become a fossil?
Rapid burial and hard parts
Index fossils allow geologists to
Match rocks of the same age in
Radioactivity is produced when unstable nuclei
If the half life of an unstable isotope is 10,000 years old and only 1/8 of
the radioactive parent remains, how old is the sample?
30,000 years old.
Radiocarbon dating is used to date
Geologic events up to 75,000 years
Which two substances are involved in carbon-14 dating?
Carbon-14 and Carbon-12
Why is radiometric dating on sedimentary rocks usually unsuccessful?
Sedimentary rocks form from many
older rock particles
Discuss the differences and similarities between metamorphic and sedimentary
Both are types of rocks formed as a
result of the rock cycle. Both types of rock can form from the other. They
differ in the way they form. Metamorphic rocks form due to immense heat and
pressure underground, while sedimentary rocks from from compaction and
cementation of sediments.
At a temperature of 150 C to 200 C, clay recrystallizes to form the
rocks chlorite and muscovite, but silicates do not change at all. What can you
Silicates require higher temperatures
in order for metamorphosis to occur.
What causes an earthquake?
Rock along a fault line bends as
stress is put on it. When stress reaches a high enough level, the rock slips or
breaks along the fault. This releases stored energy as seismic waves.
Describe how different types of seismic waves affect the movement of the
ground they pass through.
P waves compress and expand material
through which they pass and create a back and forth motion along the surface
that makes the ground buckle and crack. S waves shake material at right angles
to their direction of motion, making the ground shake up and down and sideways.
One type of surface wave moves the ground from side to side, while another type
moves along the surface like rolling ocean waves.
If you know the distance of an earthquake center from three seismic
stations, how can you find the exact epicenter of the earthquake?
On a map, draw a circle around each
seismic station that represents the distance of the epicenter from each
station. The point where the three circles intersect is the epicenter.
Can scientists make long-range earthquake predictions? Explain your answer.
Yes, they can use historical records
and measuring devices and study seismic gaps. However, the predictions are only
Why do seismic waves change directions as they pass through Earth?
Seismic waves change directions as
the waves pass through areas of different compaction or density.
Summarize Alfred Wegener’s hypothesis about past movements of the
About 200 million years ago, the
supercontinent called Pangea broke up into smaller continents that began
drifting to their present positions.
Using what you know about plate boundaries, explain the tectonic movement
that is occurring at the East African Rift valley and predict how the area will
change in the future.
The East African Rift Valley
represents the spreading that is occurring at a diverging plate boundary. In
the future, the rift valley will continue to spread and will ultimately become
an ocean basin.
Discuss the similarities and differences between oceanic-oceanic and
continental-continental convergent boundaries.
Both are convergent boundaries and
involve subduction of the oceanic lithosphere. The oceanic-oceanic boundary
creates volcanic activity. The continental-continental boundary creates
What is an unconformity?
It represents a long period of time
during which deposition stopped, erosion removed previously formed rocks, and
then deposition resumed.
How does radiometric dating work?
Geologists know the rates of decay
for many isotopes. For any rock or mineral sample that contains one of these
isotopes, they can compare the ratio of the amount of the parent isotope with
the ratio of the amount of the daughter products to find the sample’s age.
Can scientists use radiocarbon dating to find the age of a very tall, living
Scientists cannot use radiocarbon
dating because it works only on dead organisms. When an organism is alive, the
ratio of carbon-14 to carbon-12 remains constant. When it dies, the amount of
carbon-14 increases as it decays. Comparing the ratio of carbon-14 to carbon-12
allows scientists to determine age.
Explain the rock cycle by describing how an igneous rock can become a
sedimentary rock, then a metamorphic rock, and then an igneous rock again.
An igneous rock can go through
weathering and deposition to become eroded pieces of sediment, and when those
sediments compact+cement, they become sedimentary rock. THe sedimentary rock
can then become metamorphic rock if put under immense pressure and heat. If the
metamorphic rock becomes buried deep beneath Earth’s surface and melts into
magma, the magma would harden and become igneous rock again.
How can the movement of plates under the ocean’s surface have an effect on
coastal land features?
The movement of plates on the ocean
floor can cause a tsunami, sending a huge tidal wave onto shorelines. The wave
can cause or worsen erosion of coastal features such as beaches and cliffs. It
could also destroy human-made structures at or near the coast.
Explain the tectonic processes involved in seafloor spreading. At what type
of plate boundary do these processes occur?
Seafloor spreading occurs at
divergent plate boundaries. Magma rises and forces crust upward. This causes
pieces of the continental crust to crack and pull apart. Some slabs of the
crust sink, causing a rift zone. If the lithosphere continues to spread, a
narrow sea can form. Continued spreading produces an ocean basin and ridge
Faults in which movement is horizontal and parallel to the strike of the
fault surface are called
An example of folded mountains can be seen in
The Alps in Europe
In a typical fault-block mountain…
Large blocks of crust are uplifted
along normal faults.
At a continent-continent convergence,
folded mountains result
Name the three types of faults
Normal, Reverse, and strike-slip
Name the three types of stress
Tension, Compression, and Shearing
What is a hanging wall?
The block of rock that lies above
What is a foot wall?
The block of rock that lies below
Plate movement can change a flat plain into landforms such as…
Anticlines, Synclines, folded
mountains, fault-block mountains, and plateau
Which of the following is true about rocks?
Most rocks are a mixture of minerals
Which of the following is NOT one of the three types of rock?
Metamorphic rock forms as a result of
Heat and Pressure
All of the energy that drives Earth’s rock cycle comes from
Earth’s interior and the sun
The rock cycle includes all of the steps EXCEPT which of the following?
a. Magma or Lava cools
b. Sediments melt deep beneath Earth’s
surface – correct
c. Extreme heat and pressure form metamorphic rocks
d. Rocks at Earth’s surface are broken down into smaller pieces
A rock that forms when magma hardens beneath Earth’s surface is called an
intrusive igneous rock
Lava that cools so quickly that ions do not have time to arrange themselves
into crystals will form igneous rocks with a
A conglomerate is a rock that forms as a result of
Compaction and Cementation
Which of the following represents the correct order of the processes
responsible for the formation of sedimentary rocks?
Weathering, erosion, deposition,
Fossils are found only in
Sedimentary rocks with ripple marks suggest that the rocks formed
Along a beach or stream bed
Most metamorphic processes take place
A few kilometers below Earth’s
A foliated metamorphic rock forms when crystals
Combine and form visible bands
A metamorphic rock can be classified according to its
Texture and composition
What is a fault?
A fracture in Earth where movement
Wegener’s continental drift Hypothesis stated that all the continents joined
together to form
One major supercontinent called
Rocks record geologic events and
Life forms of the past
What is an Earthquake’s epicenter?
The place on the surface directly
above the focus
Most earthquakes are produced by the rapid release of which kind of energy
stored in rock subjected to great forces?
A seismogram shows that P waves travel
Faster than S Waves
Which of the following is NOT a characteristic of S waves?
a. They travel slower than P Waves
b. They are also called longitudinal
waves – correct
c. They shake particles at right angles to their direction of travel
d. They cannot be transmitted through water or air
A travel-time graph can be used to find the
Epicenter of an earthquake