Tsunami
Mass Wasting
Streams and Floods
Coastal Process
Global Climate Change
100
What is required to start a tsunami?
There must be a vertical displacement of a large volume of water to start a tsunami. This includes a vertical fault shift on the seafloor (dip-slip style seaquake), massive landslides into or under water, impact events such as an asteroid collisions, an underwater eruptions.
100
Define a watershed
A watershed is all the land area that collects water ina particular stream. It's boundaries are the boundaries of the drainage basin for that stream, also called divides because they divide the water that flows to that stream from another. Each stream is part of a subwatershed of the stream it drains into.
100
Which suffers more erosion, a headland or a bay and why?
Headlands experience more erosion because the waves are refracted around the protruding land masses. This focuses the wave action on the headland and away from the bays.
100
Identify several effects of climate change.
Climate change may cause: sea level rise (inundation of coastal areas) alterations of the biosphere (mass extinctions, migrations) desertification (loss of productive soils, loss of vegetation, loss of water supplies) changes in climate patterns (extreme/unpredictable weather events)
200
How are tsunami deaths prevented by using a monitoring system?
The DART and other buoy systems are used to collect data on sea level around the Pacific ocean and other areas that are prone to tsunami. In deep water the tsunami waves are not perceptible to people but comparison with normal data from the buoys shows when the waves pass. The speed of the wave allows a prediction of when it will impact a land area. Satellites collect data from many buoys. Although they travel up to 700 mph, the Pacific is huge so there is typically time to warn people away from beaches and low lying areas (in developed countries). Careful warnings must be given because the first wave is not always the largest and the waves may be separated by hours. Tsunami themselves cannot be prevented.
200
List some factors that determine the shape of a slope.
Some factors that determine the shape of a slope include: rock and soil type (hard rock versus soft soil) amount and type of vegetation climate (temperature variability and amount of water)
200
Streams meander in low gradient areas such as near their outlet. Why does the meander shape develop?
Meanders develop because the flow traveling the outside of a curve must travel a little faster than the water at the inside of the curve. Since faster moving water can erode more sediment, the outside corner erodes forming a cutbank. On the other hand, slower moving water deposits sediment so the inside corner builds up a point bar.
200
What is the swash zone?
The swash zone is the area of the beach that is covered and uncovered in each wave. Once the wave crashes it runs up the beach and then retreats back toward deeper water. Int his area sediments are rolled along the bottom ina zigzag pattern.
200
Explain why we have ocean and atmospheric circulation patterns. Are these patterns fixed in time and space?
Ocean circulation patterns arise as a mix of temperature and salinity currents. Cold water is denser and salty water is denser so the oceans become stratified with cold salty water at deeper locations. However, when there is a land mass such as a continent in the way mixing occurs. Air circulation patterns arise as a combination of air temperature and pressure. Hot air rises, but as it does the air pressure becomes lower below the hot air mass and fresh air rushes to fill the space. Also, as the hot air rises it is cooled and eventually the moisture in the air mass condenses forming rain. Bands of rising and falling air masses occur beginning at the equator. Air and ocean circulation patterns are not fixed in time and space but they have been stable for a long time giving us the climate zones we are familiar with today.
300
What causes the most deaths in a tsunami event?
The tsunami itself causes many traumatic injuries, sweeps many out to sea, and buries many under mud. After the tsunami additional deaths occur due to structural failures, lack of access to emergency medical care since tsunamis typically affect a large area at once, starvation, and exposure to the elements. However, the single largest killer after a tsunami is waterborne disease. Mosquitoes thrive in the stagnant water left in the inundated areas. Also, the standing water is unsanitary due to debris (including decaying biological matter such as plants, animals, and fish). Finally, clean drinking water is not available due to the salt water contamination of surface water bodies and shallow aquifers so many people drink contaminated water to stay hydrated.
300
What are the two forces in balance on a slope?
The driving force is the component of gravity in the direction of the slope. The resisting force is the friction resisting the movement due to gravity. The safety factor is the ratio of resisting to driving forces. A safety factor less then 1 indicates a slope likely to fail.
300
What is a flood? What is the floodplain? How often does the average river flood?
A flood occurs when the river stage exceeds the elevation of the river banks. The floodplain is the area adjacent to the river channel that is filled with water when the river exceeds its banks. Most rivers reach bankfull conditions with the 18 month event.
300
Why are coastal retention structures considered temporary erosion control measures?
Structures like jetties, breakwaters, and groins all retain sand by creating an area of slower flow that interrupts longshore transport. So, sand accumulates on one side of the structure while on the other side there is increased erosion because the water has the capacity to carry a set amount of sediment and that capacity is unfilled if sediment is dumped on the upstream side. Periodically the erosion control structures have to be maintained by redistributing the sand.
300
The energy balance of the earth is a critical component of global climate. Explain why the atmosphere is critical in the global energy balance.
Incident radiation from the sun enters the atmosphere as white light. However, only 45% makes it to the Earth's surface because of the UV shielding provided by the atmosphere. Once the sun's rays are absorbed by Earth, they are re-radiated as infrared light (heat). The atmosphere acts as a blanket insulating us from excess heat loss to space. However, if too much heat is retained, the climate will be altered.
400
If tsunami are relatively rare events, how do we know they tend to occur in certain places?
Because the principle of Uniformitarianism says that earth processes have occurred in similar ways under similar conditions throughout history, we know that vertical displacement of ocean water was likely to cause tsunami in the past as well. So we can study the historical coastlines of places such as Banda Aceh, Indonesia to see if there is a record of tsunami. In this location, the coastal sediments show alternating layers of clean soils growing plants for a long period of time interrupted by debris filled ocean soils. This indicates that this area is subjected to tsunami fairly regularly.
400
Explain how to much or too little water is a problem on slopes.
Water must be in balance. Too little water leaves soils dry and crumbly. The particles do not hold together and slopes fail in a fall or slide. Just right amounts of water create cohesion between soil particles because the surface tension of the water that is in films between the solid grains pulls particles together. If this type of soil fails it is usually in a slump where large blocks hold together. Too much water floods the soil pores and allows the slope to fail in a flow.
400
As a stream channel moves from its source to its outlet, how does it change?
The depth, width, and velocity increase. The slope decreases (as the river erodes to it's base level) The river tends to be more straight and rocky at the source and more meandering and sandy at the outlet.
400
When is a coastal property considered worthless?
Throughout most of the United States a coastal property losses it's value when 1/2 of the original plot has eroded. Coastal erosion rates can be as high as 10's of meters per year.
400
What is the precautionary principle?
The precautionary principle says that we should take action to avoid a possible negative consequence even if we do not have all the information to make a decision because waiting for the information could increase the negative consequences.
500
How does a tsunami wave differ from a wind driven wave?
A tsunami is caused by displaced water. In the deep ocean the wave is broad but not very tall. As the wave moves onshore, the wave slows and grows, producing a wall of water moving under its own momentum. Tsunami waves do not crash on the beach like a wind driven wave but rather continue to inundate great distances onshore. The first part of the wave may be the trough which will make the water appear to draw back an unusual distance out to sea exposing the beach.
500
Describe some factors in landslide development.
Water distribution is critical. Soils need enough but not too much water. Also, water is very heavy. Vegetation increases cohesion of soils because roots hold soils together but plants also add weight. landscaping that adds or removes reinforcement from the toe area on slopes can increase or decrease the tendency to landslide. Structures and infrastructure (roads etc.) add weight to slopes.
500
Explain why flood control structures can sometimes do more harm than good.
Flood control structures like levees can disconnect a river from its floodplain. The floodplain is necessary to hold excess flow during flood events. If there is no where for the water to go it simply rises higher and higher in the river channel. Once the control structure is breeched by the high water, the area is flooded. In many cases, the engineered channel is narrower than the natural floodplain and homes and businesses end up being built int he floodplain. Unfortunately, these areas end up flooding nearly as frequently as the natural floodplain would have flooded in the first place.
500
What is beach nourishment?
Beach nourishment is the process of adding sediments to a beach to maintain the beach profile and size. Beach nourishment is considered a sacrificial process because the sediments will eventually erode away and need replacing. Consider that maintaining the status quo at the beach is a costly and unsustainable practice. Beaches are always in flux.
500
Summarize the process of using a scientific model.
Cause and effect relationships are built into the model (usually int he form of mathematic equations). The model is run with historic data input to see if it can back forecast historic patterns. The model is then calibrated by tweaking the relationships until it successfully takes historic data as input and produces historic patterns. Then current data or future estimates are used as input and the model is run to forecast future patterns. Sometimes the input data is hypothetical to see what the possible range of outcomes from the system may be. All in all, a model is a good tool to test the outcomes of identified relationships but it is also limited because it only produces patterns based on the cause and effect relationships built in and the data given as input.
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