Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
21 Cards in this Set
- Front
- Back
|
Ground Subsidence
|
Subsidence is the motion of a surface as it shifts downward relative to sea-level
|
|
|
How is substidence related to ground water
|
Often removing water can drop the water table, As water table drops, the aquifer compacts, causing subsidence of land surface
|
|
|
How can one prevent subsidence when pumping groundwater from an aquifer
|
make sure the withdrawal rate is less than the recharge rate
|
|
|
Most caves form in soluble rocks, such as ________
|
limestone
|
|
|
Process of creating caves in limestone
|
1) Groundwater in fractures and bedding planes dissolves material
2) Dissolution widens bedding planes and fractures until they become cavities and caves 3)Part of cave above water table may be mostly dry 4) Cave below water table will contain water that further dissolves material, enlarging cave |
|
|
Sinkhole
|
is a natural depression or hole in the surface topography caused by the removal of soil or bedrock, often both, by water
|
|
|
Sinkhole on caves
|
A sinkhole develops over the collapsed part of the cave
A sinkhole develops over the collapsed part of the cave on the right side |
|
|
karst topography
|
Surface with sinkholes, limestone pillars, disappearing streams
|
|
|
What is the primary force acting to cause slop failure events?
|
gravity
|
|
|
Angle of repose
|
It is the maximum angle of a stable slope determined by friction, cohesion and the shapes of the particles.
|
|
|
some ways that slopes fall
|
Undercut cliff
Earthquake activity Too steep a slope Landslide Undercut slope |
|
|
what factors control slope stability
|
Angle of repose for material
-Loose materials, like soil may have typical angle of repose; solid rock can hold steeper slopes Discontinuities: fractures, cleavage and bedding -Rock is weaker if discontinuities are oriented so rocks can slide downhill Amount of water -Adding too much water to loose materials can weaken them |
|
|
some events that could trigger slope failure
|
Precipitation
Volcanic Activity Sudden shock, as from an earthquake Changes in land uses Undercutting slope Overloading slope |
|
|
Classification of Slope Failures
(3) (2 in each) |
Movement: fall or flow
Type of Material: Unconsolidated or solid rock Rate of movement: fast or slow |
|
|
Rock fall and debris fall
|
must be a cliff; large blocks below cliff may indicate the potential for fall
|
|
|
Rock slide
|
somewhat intact block at start of movement; typically detaches along bedding plane, fault, or other discontinuity
|
|
|
Rotational Slide (slump)
|
curved surfaces in either rock or loose materials; also called a slump
|
|
|
Creep
|
slow, continuous movement in weak materials; occurs on most slopes but at different rates
involve flow |
|
|
Debris slide
|
involves flow
Unconsolidated but detaches along some interface |
|
|
Earth flow
|
involves flow
weak, with matrix of fine-grained materials; moves like wet concrete; also called mudflow |
|
|
Northern Indiana doesn’t show a widespread risk of landslides
at this scale on this map. Does this mean we can completely forget about it? |
No! Our problems are more local in scale and don’t show
up on a national map |
