Week 12, Floods and Impacts from Space Flashcards
Rainfall floods
Occur due to precipitation that exceeds ability of river
Slow rainfall floods
Sustained heavy rains
Flashfloods
Thunderstorms, intense and fast
- rain event is larger than the bearing capacity of the soil
- fatalities often related to driving through flood intersections
- most common in desert areas because dry soils won’t absorb water
Why was the Alberta 2013 flood considered to be the flood of floods?
- largest evacuation in Canada in the past 60 years
- triggered by significant rain
- large mountain snowpack, high ground water table
- wet spring saturated soils
What kind of flood is the most common in Canada?
Snowmelt flood
Rain on snow flood
Combine rainfall and snow melt events. Rain causes even more extreme melting.
Icejam floods
Occur mostly on rivers that flow from South to North
Accumulation of ice fragments that act as a temporary obstruction, restricting water flow. Can occur during freeze up or break up.
Natural dams can be formed by
glaciers, mass movements, or lava and pyroclastic flows.
Jökulhlaups
Glacial outburst floods
Flood frequency curves give us
historical data on floods.
Extraterrestrial impacts can be due to
Asteroids and Comets
Fragments of asteroids and comets can be referred to as
- meteoroids: before impacting earth
- meteors: while passing through atmosphere
- meteorites: after impacting earth
Asteroids
- Stoney/metallic bodies that orbit the sun
- Medium size
- Planetoids or minor planets
- Mostly in asteroid belt between Mars and Jupiter
3 smaller groups of asteroids with orbital paths that intersect orbits of Earth/Mars
Apollos
Aten
Amars
Comets
- Small bodies, highly elliptical solar orbits
- Mostly water, ice and frozen gases. With some rock and dust.
Meteorites
- Stoney fragments of a comet or asteroid
- Iron-rich
The atmosphere can protect the Earth from meteorites depending on their
size.
Simple craters
Rim, concave bottom, cause by small meteoroids.
Complex craters
Resembles water drop, impact then we experience rebound and uplift.
High temperature and pressure vaporize object and rock.
What erased evidence of crater/impact?
Weather, erosion, and tectonic processes.
What happened in the KT impact?
Mass extinction- 85% of all species were erased from the earth
How can we explain KT extinction?
Clay contain quartz grains with “shocked” structure
More Iridium in clay than usual
Mineral spherules are present indicating a melt
Radioactive element ratios similar to meteorites
