Our Dynamic Earth II Exam 2

How does precipitation factor into avalanches?

New snow amount, snow accumulation rate, new snow density, rainfall All this factors into how stable the snowpack is

Point Landslide

Starts at a single point

Where does vertical water displacement come from?

Subduction Zones and the friction and movement that occurs at these areas

Steps of the tsunami detection system? How?

1. detect an earthquake: was it a 7.5 or greater? where was the epicenter? 2. detect the rise/fall of the ocean surface (tidal gauges) 3. Detect the pressure of the tsunami wave passing (tsunameter) - Result = real-time model of the tsunami propagation - Can set up sensors within areas to detect ocean movements after earthquake hits

What is ash?

Explosive eruptive products

How does viscosity influence magma?

- how magma moves - Influenced by temperature and composition - Higher viscosity = more felsic

Which regions are at the greatest risk for tsunamis?

- regions near subduction zones - coasts of South America, Indonesia, Alaska, Hawaii, Europe, Pacific and Atlantic Islands - Areas across from subduction zones

Characteristics of the typical avalanche victim?

- snowmobiler, out-of-bounds skier, backcountry skier or climber - In colorado - During January through March - In their late teens to early 30's - In deep snow

What happens to water as it moves closer to the shore?

- the height increases - the wavelength decreases - the wave speed decreases - the velocity decreases

How are Tsunami warning systems put into place and how is predictability involved with tsunamis?

- when issuing a tsunami warning the earthquake magnitude must be considered, a warning is issued each time there is an earthquake of magnitude 6.7 or greater near a coastline or open ocean - warning systems are more effective for a distant tsunami than for a local one - predictability of the impact of a tsunami is difficult to hypothesize

Characteristics of Slide Landslide

More wet and moves more slowly

What is the wave height and wave length associated with tsunamis?

Wind-blown waves are typically less than a few meters in height, with wavelengths of no more than a few hundred meters. Tsunamis, by contrast, have extremely long wavelengths, sometimes hundreds of kilometers in the open ocean, although their wave height is often smaller than a wind-blown wave

How does could cover and radiation factor into avalanches?

clear skies vs. covered or night skies affect exposure to solar radiation and heat, more exposure makes snowpack unstable and prone to movement/melting

Characteristics of Pillow Lava?

comes up under water, cools instantly

How do these events create tsunamis?

The displacement of water associated with these events creates a huge bulge of water above sea level, gravity then forces the bulge back down to the ocean's surface and water is pushed outwards in a rapid series of concentric waves that travel rapidly over the ocean's surface until they make it to the coastline where this tsunami wave gets taller as the shore becomes shallower.

Characteristics of 'A'ā Lava?

slow moving, crumbles easier, high velocity, surface lava

How does wind factor into avalanches?

speed and direction, can cause dangerous cornices (overhangs of blown snow over ridges)

How does an earthquake rupture cause a tsunami?

the rupture in the seafloor pushes water upwards starting the tsunami, the water then moves rapidly in the deep ocean reaching speeds up to 5000 km/hr and creating a huge wave with a height greater than 1 meter

Characteristics of Flow Landslide

very wet and moves more slowly

How does a reverse fault trigger a tsunami?

water goes over, water shifts up and forms a wave

Characteristics of Pāhoehoe lava?

flows like water, surface lava

Characteristics of the Divergent Oceanic-Oceanic volcanic region?

- Decompressed magma rises through the spreading plates - Mid-Atlantic Ridge, South Pacific

Characteristics of the mid-plate hotspot volcanic region?

- Decompression of magma - Hawaii

What are the characteristics of tsunamis at the shore?

- Devastation is extreme - Length of wave is very long but when it hits the shallower water closer to shore it is slowed down due to friction - This then causes the wavelength to dramatically decrease and this large amount of water backs up and builds into a tower of create height to compensate - Then this large amount of water floods the shore

What are volcano warning signs and forecasting?

- Earthquake - Increased emission of heat and gas from vents of volcano - Inflation and swelling of volcano

How does urbanization effect landslides?

- Exacerbates hillsides by building on, under, or above - Clear Cutting: clearing vegetation - Road Cuts: destabilizing slopes

How does volatility influence magma?

- gasses (volatiles) in magma - more volatiles, the more explosive - More volatile = more felsic

Characteristics of Slump Landslide

Wet and moves more slowly

Dome (Stratovolcano): characteristics and how it relates to magma

- Higher silica content, higher viscosity, higher volatility, higher explosivity - Lava plugs up the top - Stratovolcano: - Top of the dome volcano blows out, lava plugs up the top creating a "dome: or rounded shape - Build up of the lava creates a ticking time bomb" because of heat and pressure forcing the magma chamber up

Characteristics of the Convergent Oceanic-Oceanic volcanic region?

- Island arc, many spots along the ring of fire, Aleutian islands - Volcanoes are Tall, Pronounced, and Conic Shaped

Characteristics of Mafic magma in terms of viscosity, volatility, silica content and explosivity?

- Low Silica Content - Low Viscosity = pours over surface like water - Low Volatility = not many gases - Not highly explosive

What are some strategies humans can use to survive avalanches?

- Make an air pocket in the snow - Let go of your heavy equipment - Hold an arm straight above your head - Conserve air and energy - Avalanche survival equipment - shovel, helmet, skiers airbag - "Start Swimming"

What are the human impacts on mass wasting?

- Mass wasting is the downslope movement of rock - Building on, under, above the slope - Taking away material on, above, or below a slope - Road cuts and developments or buildings

Characteristics of the Convergent Oceanic-Continental volcanic region?

- Melted magma rises - Subduction zones - Andes Mountains, North West Coast of US - Volcanoes are Tall and Conic Based

Characteristics of the Divergent Continental-Continental volcanic region?

- Mid-West Coast African Rift Valley, Iceland - Continental Asia, North America Mid-West

How does silica influence magma?

- More silica the lighter the color - More Silica, More explosive - Rhyolite or Granite = more felsic, cools slowly - Basaltic = more mafic, cools quickly

What are the effects of a Tsunami near and far from the epicenter?

- Run-up: water washes onto the shore - Backflow: water backs up which exposes the shore - tsunami comes through and then peaks - earthquake sends out through land or ocean

What factors trigger avalanches?

- Storminess - Skiers - Temperature - Winds - Slope - Terrain - Snowpack conditions - Slope avalanches

Composite Volcano: characteristics and how it relates to magma

- Taller than they are wide, more triangular - More deadly when they erupt, pyroclastic material - Higher silica, viscosity, volatility, explosivity - Subduction zones, areas with high H2O (humidity) - Smaller in size but larger in explosivity and intensity - Ash falls back down on top of lava, forms layers of sediments, creating stratified layering

Shield Volcano: characteristics and how it relates to magma

- Wider than they are tall - Mostly basalt rock - Low silica, low viscosity, low volatility, low explosivity - Hot spots and divergent boundaries - Lava flows like ketchup, pours over surface and eventually solidifies

What are the characteristics of a Distant Tsunami?

- arrives later - unexpected - occurs to a trigger farther away from an area - better warning systems and more evacuation time

What are the characteristics of a Local Tsumani?

- arrives sooner - form a nearby source - destructive effects are usually confined to the coasts within 100km or less than 1hour of travel time of the tsunami from its source - usually generated by an earthquake, can also be triggered by a landslide or pyroclastic flow from a volcanic eruption

How do volcanos cause climate change?

- during eruptions volcanoes emit a mixture of gases and particles into the air - ash and sulphur dioxide have a cooling effect because they or the substances they cause reflect sunlight away from the earth which cools the earth - co2 affects warming (greenhouse gases)

Types of Volcanoes

Shield, Composite, Dome (Stratovolcano)

Slab Landslide

A big area breaks off, and slides downslope like a "slab"

What is Pyroclastic Material?

A dense, destructive mass of very hot ash, lava fragments and gases ejected explosively from a volcano and typically flows downslope at a great speed

What is Pyroclastic Flow?

A dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically downslope at a great speed

What is Lava Flow?

A mass of flowing or solidified lava flow

What are the characteristics of an Inland Tsunami: The Run-Up and Run-In?

A tsunami's impact on a coastal community is usually described by two measurments: Run-Up: the maximum height of a tsunami above sea level Run-In: the distance the rising water moves inland from the normal coastline sometimes the trough of the wave approaches the shore first, leading the sea to actually get lower and therefore pull away from the shore and then when the wave arrives the water rushes in again

How does a normal fault trigger a tsunami?

A vertical displacement of water that then trigger a wave that pushes back to fill space

Characteristics of Rockfall Landslide

Dry and fast moving

Creep Landslide

Dry and moves very slo

What are the different causes of Tsumanis?

Earthquake Rupture, Volcanic Eruptions, Massive Landslides, Meteor Strikes

What events trigger tsunamis?

Earthquakes of at least 7.5 magnitude, underwater landslides, underwater volcanic eruptions, meteorites (comets and asteroids)

Characteristics of Felsic magma in terms of viscosity, volatility, silica content and explosivity?

High Silica Content High Viscosity = flows like honey High Volatility Highly explosive

Whats the most common tsunami trigger?

Large earthquakes, which cause a rapid uplift or subsidence of the seafloor - Most tsunamis are caused by earthquakes generated in a subduction zone, an area where an oceanic plate is being forced down into the mantle by plate tectonic forces. The friction between the subducting plate and the overriding plate is enormous.

How is magma different than (surface) lava?

Magma is under the surface and comes from pockets close to Earth's surface, rather than lava which flows over Earth's surface

Primary vs secondary volcano hazards: Examples and differences. Which are most deadly?

Primary: - pyroclastic flows, air fall tephra, lava flows Secondary: - ground deformation, lahars, landslides, even tsunamis - more deadly

Resisting vs. Driving (Downslope) forces and determining factors?

Resisting: - Vegetation, bed planes, stabilizing walls Driving: - Clear cutting, development, road cuts, storms, moisture

Which types of Faults trigger tsunamis?

Reverse Faults and Normal Faults

What is tephra?

Rock fragments and particles ejected by volcanic eruption, regardless of composition, the fragment size or their emplacement mechanism

What is a wave period associated with tsunamis?

The wave period associated with tsunamis is in the order of minutes or hours (compared with seconds for wind-blown waves), and so successive tsunami waves may hit a shoreline with many minutes in between. - Amount of time between wave crests

Which types of faults do not trigger tsunamis?

Transform faults do not because there is no vertical displacement of water

Types of slopes

Upper Convex, Straight, Lower Concave, Free Face, Talus

What is Lahar?

Volcanic mudflow created when water (from rain or meltwater glaciers) and ash mix or occurs after a long volcanic eruption

How does temperature factor into avalanches?

rising and fall in temperature makes snowpack unstable because of the fluctuation