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What Problems Are Caused by Landforms?

The topographic features called landforms, sculpted by numerous physical agents such as tectonic collisions and running water, lend scenery to the surface of the Earth. They can also cause problems for the human beings living on and around them, not least because they are, in a sense, "alive" -- subject to active expressions of the forces that created them.

Flood Plains
- A river's floodplain is occasionally inundated by backwater.
  
  A mature, meandering river builds a flood plain along the shoulders of its channel. Usually bound by terraces, flood plains are built up by sediment depositions during periods of high flow, when rivers jump their banks and spill out upon these flat lowlands. When homes and businesses lie on such landforms, they are subject to inundation by muddy, swollen backwaters. This happens frequently during spring snowmelt and high precipitation in the U.S. Midwest and South.
Volcanic Eruptions
- An eruption of the stratovolcano called Mount Vesuvius destroyed the Roman city of Pompeii.
  
  Volcanoes are among the most dramatically violent of the planet's landforms. A variety of volcano types exist, defined by the type of molten material they emit and their resultant shape. Some, like the archetypal conical mountains called composite or stratovolcanoes, can be terrifyingly explosive. Their lava, debris flows and ashfalls can all be a threat to life. The Roman cities of Pompeii and Herculaneum were famously destroyed by the stratovolcano Mount Vesuvius in 79 A.D. Some of the most dangerous conditions arise on glacier-clad volcanoes such as Washington's Mount Rainier. Lava ejections from such volcanoes melt snow and ice to form a fast-moving, smothering pyroclastic mudflow called a lahar.
Avalanches
- The fast-moving tongue of snow and ice in an avalanche can be life-threatening.
  
  A sheer mountainside can cause problems for backcountry activities such as skiing, snowshoeing and mountaineering because of the threat of avalanches. These are surging masses of snow and ice that dislodge from a mountain snowpack and hurtle downslope with terrifying speed and power. They are triggered by events that destabilize banks of snow, such as a rapid warming of air temperature or a shift in a spring storm from snow to rain. Large avalanches can be more than 10 feet deep and 1 mile across, and can plow ahead at speeds greater than 80 mph. Winter travelers in the mountains need to be well aware of snow conditions to avoid being caught in avalanches, which can easily overtake and kill the unwary traveler. Like many such events, avalanches also exert a positive ecological influence, creating habitat diversity and operating as an agent of succession, the cycle of vegetation communities that help define an ecosystem.
Sinkholes
- Sinkholes vary widely in size.
  
  Areas underlain by carbonate rocks, especially limestone and dolomite, can develop so-called karst landscapes because of the bedrock's tendency for chemical weathering. Caves, tunnels and monolith formations are among the resulting landforms. Another is the sinkhole, where acidified rainwater and groundwater excavate a cavern in underlying carbonate rock into which surface sediments eventually collapse. While many sinkholes are relatively small, some are large enough to swallow entire structures. They are a building hazard in areas such as Florida, which has a limestone peninsula.

Nature