TSUNAMIS
- About
- Series of fast-moving waves that send surges of water on to land.
- Caused mostly by underwater earthquakes, but also by underwater volcanoes and landslides. The ground moves up and down quickly and energy is transferred to the water, much like if you push a beach ball up and down in the water creating waves (just a heck of a lot bigger).
- About 80% happen in the Pacific Ocean's "Ring of Fire"...a very tectonically active area where volcanoes and earthquakes are common. You can watch a video about the Ring of Fire here.
- They can move at 800+ km/hr (500 mi/hr)...but may not be felt by boats on the deep water since they do not build tangible height until they near the coast.
- Water will recede from the shore as it approaches the coast, build a giant wall of water, where the top moves faster than the bottom. Seeing this can warn inhabitants of impending danger, as it usually occurs 5 minutes before the tsunami hits.
- Some tsunamis do not appear as walls, but rather surges of water inland.
- Usually occurs in series...so threat may not be over after initial surge.
- Devastation occurs however far the tsunami reaches inland, as the water cannot be stopped and is very heavy. It can take down whole building, bridges, and cause massive loss of life.
- Management
- Like all natural disasters, we cannot stop tsunamis from happening. They are actually a part of Earth's ntural recycling effort...but that does not mean we cannot protect ourselves from potential human catastrophe. The best thing we can do is prepare residents and buildings of areas that are in the most danger of being affected. How we do this now is to:
- Have buildings in those areas built to a code that should withstand the force of a tsunami.
- Use sensors attached to the seafloor to detect ocean wave speed and warn those that may be in its path (below is a graphic of these...signal sent to sattelite, then to cities in danger)
- Educate residents of danger areas to evacuate when advised or to flee if they see a water in a coastal area receding quickly and/or abnormally.
- World rescue organizations are able to provide relief...however, education and warning are the biggest help in reducing the negative impact of tsunamis.
LANDSLIDES
Watch the following video to learn about landslides:
Key points to remember:
- Uncontrollable flow of rock, earth, debris, or all 3 caused by earthquakes, excessive rain, erosion, etc.
- Speed determined by material and slope...loose rocks flow fastest (up to 200 mph)
- Slow moving earth, known as soil creep, can be caused by frost, rain loosening up soil, or animals
- It is so slow, that humans have to look for cracks in pavement, leaning power lines, or other destruction to see if it is happening
- Landslides that dump into water can cause tsunamis (has happened in areas behind dams)
- Landslides involving rocks happen in a chain reaction fashion...one or a few rocks falling loosen others, which may be bigger and more destructive
- Slumps - earth moves due to excess groundwater, causing the earth to sink in and move down a slope
- Debris slides - as material falls down a slope it takes other material with it causing huge losses
Management
Landslide management takes place by knowing which areas are most susceptible and what causes them. The basic things that can be done are:
- Drainage correction (decrease water buildup)
- Proper land use measures
- Reforestation for the areas occupied by degraded vegetation (decrease erosion)
- Creation of awareness among local population (let people know the signs)
GROUND DEFORMATION
Happens at sites of volcanoes and can let us know what is happening at that site...possibly warning of eruptions or other activities. See the techniques used to determine the severity here (make sure to click the different techniques on the left).
VOLCANIC ASH
Go to the USGS website here. Please click the links on the top to learn more specifics on volcanic ash, they give great information you may need on what volcanic ash is. Also, the many links on the right can let you know what it's like when it falls, and what we can do before, during, and after a volcanic ash event. There are also many case studies that you will want to peruse to use on your AICE exam.
LAVA
Please read the LAVA section on the following website to get a general idea on how to manage lava. It usually moves so slow that people can get out of the way, but because it is so hot and heavy, it can destroy buildings and anything else in its path.
LAVA link.
HOT ASH CLOUDS (NUEE ARDENTES)
Pyroclastic flows can cause major damage...there is no way to outrun them. The best management is to not be in an area of an active volcano. This site gives a good description of pyroclastic flows (hot ash clouds) and how to best manage in the events.
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