Natural Disasters and Plate Tectonics (L33)

Question 1

What is an important thing to keep in mind about natural disasters associated with geological processes?

Answer 1

they are natural

Question 2

What is an earthquake?

Answer 2

A sudden release of stored energy caused by slip along a fault or fracture in the earth

Question 3

What are major earthquakes caused by?

Answer 3

Slow deformation and buildup of energy between tectonic plates

Question 4

What is the Focus?

Answer 4

the point of energy release or rupture underground

Question 5

How is energy built up and then released?

Answer 5

we start with rocks on both sides of an existing fault that are deformed by tectonic forces

once frictional forces along the fault are overcome, slippage occurs at the weakest point (the focus)

an earthquake occurs due to this release of energy as seismic waves when the deformed rocks springs back to its original shape (elastic rebound)

Question 6

What 2 categories do Seismic waves belong to?

Answer 6

Body waves that travel through the material

Surface waves that travel on Earth’s surface and produce most of the shaking

Question 7

What are the 2 types of body waves?

Answer 7

Primary (P) waves have a push-pull
Secondary (S) waves are characterized by shear motion at right angles to their direction of travel

Question 8

What difference do P waves and S waves have in traveling?

Answer 8

P waves travel through all states of matter
S waves travel only through solids

Question 9

What are the 2 surface waves that travel on the surface?

Answer 9

Rayleigh waves - move in a rolling motion
Love waves - move side-to-side

Question 10

What instrument is used to record seismic waves?

Answer 10

Seismometer

Question 11

What is the graphic representation of the detedction of seismic waves by a seismometer?

Answer 11

Seismograph

Question 12

How do you determine the distance between the recording station ad the earthquake’s epicentre?

Answer 12

Differences in the arrival times of these waves at different recording stations

longer the time diff betewen the arrival of hte first P waves and the arrival of the first S waves, the greater the distance between the recording station and the earthquake epicentre

Question 13

about 95% of the energy released by earthquakes is focused along _____

Answer 13

Plate boundaries

Question 14

What is magnitude?

Answer 14

basically is a quantitative measure of the amount of energy released during an earthquake

Question 15

What is Richter magnitude?

Answer 15

A concept where units of magnitude are based on the amplitude (wave height) of the largest seismic waves recorded, and also accounts for the decrease in wave amplitude with increased distance from the epicentre

Question 16

Where does the word tsunami come from?

Answer 16

Japanese “tsu”, meaning harbour and “nami” meaning wave

Question 17

How do Tsunamis result?

Answer 17

result from a signficant vertical displacement of water due to the slip of a fault located on the ocean floor, a large undersea landslide triggered by an earthquake, or other disturbances

Question 18

How is a tsunami caused in detail?

Answer 18

the plate is bulging upward due to being deformed from being stuck to the subducting plate

when the plate becomes unstuck, it snaps back into an unstressed state and displaces a large amount of water at once, producing a large wave

Question 19

When do tsunamis become destructive?

Answer 19

when they travel into shallow water, due to there being friction between the moving water and the sea floor

Question 20

Why is the Japanese Tsunami termed a triple disaster?

Answer 20

because it included an earthquake, a tsunami and a nuclear meltdonw

Question 21

What is an imprtant step to reduce damage from tsunami?

Answer 21

the installation of warning systems as it can take hours for tsunami to reach distant shores

Question 22

Where do most volcanoes occur along?

Answer 22

plate tectonic boundaries

Question 23

why do volcanoes associated with mafic magmas erupt relatively gently?

Answer 23

they have a low viscosity (runny) due to low silica content and low gas content

Question 24

Why do volcanoes with intermediate to felsic magma tend to erupt explosively?

Answer 24

b/c they have high viscosity (stiff and gooey) due to high silica content and hvae high gas content

Question 25

What is a caldera?

Answer 25

the crater produced by a collapse of the top of the volcano as it is so violent and explosive

Question 26

How do explosive eruptions lower the amount of solar radiation reaching Earth’s surface?

Answer 26

explosive eruptions emit huge quantities of gases and fine-grained ash into the atmosphere which filter out and reflect a portion of the incoming solar radiation back into space

Question 27

What does sulphur doxide do during a volcanic eruption?

Answer 27

changes into sulphate aerosols, which are liquid particles that reflect sunlight and keep some of the warmth from reaching Earth’s surface

Question 28

How is volcanism tied to the art piece The Scream?

Answer 28

Munch the artist of the piece was inspired by the blood red sky he saw and drew it on the painting

this red sky was due to the volcano Krakatau exploding and Munch witnesse the fiery sunsets created from it