landforms from groundwater erosion and deposition

groundwater deposition

Groundwater carries dissolved minerals in solution. The minerals may then be deposited, for example, as stalag- mites or stalactites (Figure 1.4). Stalactites form as calcium carbonate drips from the ceiling of a cave, forming beautiful icicle-like formations. The word stalactite has a c, and it forms from the ceiling. Stalagmites form as calcium carbonate drips from the ceiling to the floor of a cave and then grow upwards. The g in stalagmite means it forms on the ground. If a stalactite and stalagmite join together, they form a column. One of the wonders of visiting a cave is to witness the beauty of these amazing and strangely captivating structures. Some of the largest, and most beautiful, natural crystals can be found in the Naica mine, in Mexico. These gypsum crystals were formed over thousands of years as groundwater, rich in calcium and sulfur flowed through an underground cave. Check it out: A relatively small sinkhole in a Georgia parking lot. Stalactites hang from the ceiling and stalagmites rise from the floor of Carlsbad Caverns in New Mexico. The large stalagmite on the right is almost tall enough to reach the ceiling (or a stalactite) and form a column. Click image to the left or use the URL below. URL:

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sinkholes

If the roof of a cave collapses, a sinkhole could form. Some sinkholes are large enough to swallow up a home or several homes in a neighborhood (Figure 1.3). Water flows through Russell Cave Na- tional Monument in Alabama.

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cave formation

Working slowly over many years, groundwater travels along small cracks. The water dissolves and carries away the solid rock, gradually enlarging the cracks. Eventually, a cave may form (Figure 1.2).

groundwater erosion

Rainwater absorbs carbon dioxide (CO2 ) as it falls. The CO2 combines with water to form carbonic acid. The slightly acidic water sinks into the ground and moves through pore spaces in soil and cracks and fractures in rock. The flow of water underground is groundwater. Groundwater is described further in the chapter Water on Earth. Groundwater is a strong erosional force, as it works to dissolve away solid rock (Figure 1.1). Carbonic acid is especially good at dissolving the rock limestone.

instructional diagrams

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questions

much of the work of erosion at a shore is done by

a) longshore currents

-->  b) waves

c) rip currents

d) rivers

shorelines are often straight because

a) waves come in parallel to the shoreline.

b) longshore currents erode in a fairly straight line.

c) waves come in perpendicular to the shoreline.

-->  d) wave refraction concentrates or disperses energy.

the erosion of a sea arch can form this.

a) cliff

-->  b) sea stack

c) beach

d) sea wall

a long, narrow pile of rocks built perpendicular to the shoreline to keep sand t the beach.

-->  a) groin

b) seawall

c) sea stack

d) breakwater

a long, narrow bar of sand that form parallel to the shore by wave transport of sand is a

a) beach

b) groin

-->  c) barrier island

d) spit

a shorelines first line of defense against hurricanes is

a) beaches

b) lagoons

c) spits

-->  d) barrier islands

a length of sand that connects to land and extends into the water, with a hook at the end is a

a) spit

-->  b) tombolo

c) barrier island

d) groin

the problem with groins is

-->  a) they starve the beach down-current of them of sand.

b) they starve the beach up-current of them of sand.

c) they are easily taken out by a rogue wave coming in perpendicular to the shore.

d) they are often knocked down by long-shore currents.

engineers can build structures that will protect our shorelines, come what may.

a) true

-->  b) false

compared with the sand on a low energy beach, the sand on a high energy beach will be

a) a mixture of minerals, rock fragments and shells.

b) mostly shells.

-->  c) mostly hard minerals like quartz.

d) its impossible to say.

diagram questions

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