EAE 12 - Landslides, Tsunamis and Impacts Flashcards

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1
Q

What are Landslides?

A

A landslide is a gravity-related slope failure.

Slopes are a consequence of a dynamic planet (landforms change due to tectonic forces).

Over geologic time – slopes are not stable and change constantly.

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2
Q

What is Solifluction?

A

Downward movement of wet soil along the slopes under the influence of gravity

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3
Q

What is creep?

(In context of Earth movement)

A

Creep is extremely slow downward movement of dry surficial matter in regions which are subjected to freeze-thaw conditions.

Creep < 2m

Rapid flow ~5m

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4
Q

What is ‘Subsidence due to collapse’?

A

Subsidence that occurs due to:

  • extensive pull out of large volume of underground water
  • (In limestone terrain) subsurface solution activity

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5
Q

What is plastic outflow subsidence?

A

When a plastic layer like clay bed is squeezed outward due to overlying heavy load

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6
Q

What are slump blocks?

2 points.

A
  • Large blocks known as a slump blocks move during a landslide.
  • Common
    • After earthquakes
    • After removal of part of the slope due to construction (particularly for construction of roads).

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7
Q

What are debris flows?

A

Debris flows often occur after heavy rain falls.

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8
Q

What are the main factors that contribute to landslides?

6 points.

A
  • Slope
  • Water content
  • Geological structure
  • Unconsolidated or loose sediments
  • Lithology
  • Human interference

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9
Q

What are triggers for slope failure?

3 points.

A

The steepness of a slope does not defineits stability.
The geology does.

  • shaking grounds (cf. Liquefaction)
  • Excess precipitation
  • Removal of vegetation can be an additional factor.

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10
Q

How does water impact on stability?

3 points.

A

Super-saturated sediments will fail.

  • Dry sand: friction and cohesion provide shear strength
  • Saturated sand: friction and cohesion still sufficient to give the sediment strength.
  • Super saturated sand: The fluid supports grains. Shear strength is zero → sediment deforms and fails.

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11
Q

What is the effect of vegetation?

3 points.

A
  • Vegetation gives slopes additional stability
  • The effect is critical because water levels are kept lower
  • The chance of ‘pore pressure > friction’ is drastically reduced

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12
Q

How are tsunami initiated?

2 points.

A

A Tsunami is triggered by the sudden displacement of large water masses in the ocean.
The energy is transferred into waves.

  • Most frequently: Earthquakes (when the ocean floor is lifted or drops quickly)
  • Alternatively: Under-water landslides

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13
Q

What initiates a tsunami?

A

Water displacement is triggered by an undersea earthquake. A tsunami wave is created (greatly exaggerated). Energy is transmitted from the earthquake into the water.

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14
Q

What happens immediately after a Tsunami is initiated?

A

The tsunami is split into a distant tsunami and local tsunami with the height of both being each half of the original one.

Both travel in opposite directions. The speed of both tsunamis varies as the square root of the water depth

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15
Q

What happens as a Tsunami progress?

3 points.

A

The local tsunami will

  • reduce in wavelength
  • increase in amplitude

There is a trough in front of the tsunami (retrieving water), followed by a strong wave (incoming tidal wave).

The distant tsunami has travelled farther.

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16
Q

What is the tsunami run-up?

4 points.

A

The tsunami run-up is the waterfront above the normal water level.

  • Usually, waves don’t break (unless it is a gigantic tsunami).
  • Tsunamis do not stop on landfall and travel far inland.
  • The first wave may not be the largest
  • Edge waves (think of a fan of waves hitting a straight coastline) result in different travel times.

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17
Q

What are the key dangers of Tsunami?

4 points.

A
  • Tsunami waves do not break – they are continuing waves that travel inland with a continues powerful flow
  • Behaivour is similar to the tides (which is a type of wave)
  • A critical danger is the retreat of waves, which can carry debris out at sea.
  • Tsunamis can come in a series of waves!

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18
Q

What determines the outcome of shooting stars?

A

Depending on angle of fall (crossing the atmosphere), the object may burn or make it through.

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