southeastern Missouri
Rainwater falling on bare soil is quickly concentrated into rills that are responsible for substantial soil erosion.
Rills can grow into larger gullies that not only erode soil, but are much harder to repair.
Gullying of soils and weak sandstone. This is an extreme case of erosion caused by a combination of strong thunderstorms and historically poor agricultural land management.
Ice crystals that form overnight in the soil push small rocks and soil particles upward. As the ice melts, gravity will pull these particles down slope as part of the slow mass wasting process called "creep."
Close up of the ice crystals.
The curved tree trunks result from soil creep.
Small slope failures (mudflows) are common in this landscape of steep slopes, wildfires, dry summers, and rainy winters.
A debris flow will often leave behind a distinct channel and lobes of rocks and other sediments at the end of the flow.
Lake
Michigan near Milwaukee, Wisconsin
The steep bluffs along the Lake Michigan shoreline are highly susceptible
to erosion and mass wasting. The bluffs are about 120 feet high and are
undercut by waves during periods of high lake levels.
Slumping of loose, unconsolidated sediments. Note that intact blocks of material have moved from the top of the bluff and are sliding down the slope--the red sumac originally grew at the top of the bluff.
A rockslide has delivered these boulders from there original position on the steep slopes above.
Mass movements have deposited fans of material into this narrow alpine valley. At one time, this rock slide dammed the small river in the foreground and flooded a small village.
Mass movements have deposited fans of material into this narrow alpine valley.
Early 20th century coal mining practices often left such unstable “highwalls” in the landscape. Subsequent rockfall has produced the talus at the base of the cliff.
Rockfall is responsible for the large boulders at the base of this cliff.
The Las Casitas debris flow occurred on October 30, 1998 as a result of torrential rains from Hurricane Mitch. A crater lake at the top of Volcan Casita (1405m) filled until it spilled over the edge of the crater, initiating a debris flow of 200,000 cubic meters of volcanic ash, cinders, and rocks ranging from clay-sized sediments to 10m boulders. The upper path of the flow is seen in the background.
The Las Casitas debris flow extended over 15km before coming to a stop. The yellow tractor (extreme right of photo) was located half way up the slopes of Volcan Casita (background) at the time of the debris flow.
Memorial Park at Volcan Casita commemorates the deaths of approximately 2,000 people from 3 villages that were covered by the debris flow.
This dry river bed is filled with sediment from a very liquid mudflow that traveled down the river valley (note ripple marks in sediment). In the background, civil defense personnel are training for disaster evacuation.
Suburbs have rapidly expanded beyond the old city, resulting in a large commuter population.
This road provided the only direct access to Quito for thousands of commuters before the slope failed in 2003.
The geologic material is volcanic ash. Note that below the water table (essentially the elevation of the waterfall) the ash is saturated.
View downstream from the same site. The deep river canyon has undercut the bluffs, making the slope below the road even less stable.
