Geology Reference
In-Depth Information
Changing Coastlines
Another way humans act as geologic agents along the coast is by building seawalls and
manmade
spits
(linear deposits of sand) to direct the flow of water and sediments in or-
der to minimize the removal of beach sand by wave action. The goal is to maintain a
beachfront for the homes and other structures that have been built. However, these
structures actually reduce the natural beachside drift of sediments. In some cases, the
manmade structures also concentrate and magnify wave energy — resulting in increased
erosion of beach sediments and leading to the need for more beach nourishment, not
less.
Destabilizing Slopes
The surface of the earth is not flat. Humans cannot help but construct building on slop-
ing surfaces, ridgetops, and bluffs. By doing so, they add weight to the soil and may
overload a slope's ability to maintain, leading to a landslide.
Humans destabilize slopes and create landslide conditions in a couple different ways.
When the trees and other vegetation are removed from a surface, the sediments are no
longer securely anchored and may slide downslope as a landslide. Similarly, when hu-
mans cut through hillsides to construct roads or homes, the angle of the cut may be too
steep to support the overlying rocks and sediment.
Fracking for Natural Gas
Natural gas is a relatively clean energy source. However, to access the earth's supply of
natural gas, humans have to drill deep into the crust and break open rocks where the
gas is trapped. One process used to release the gas from these rocks is called
hydraulic
fracturing,
or
fracking.
The process of fracking begins by drilling a very deep hole into the earth's rock layers.
When a layer of rock containing trapped gas is reached, a large amount of fluid (a mix of
water, sand, and chemicals) is pumped into the hole. The high pressure of this fluid be-
ing pumped in breaks the rock, creating many tiny fractures that release gas. This gas is
then pumped to the surface and collected.
The water containing the fracking chemicals is left underground to fill the spaces in the
fractured rocks and may eventually flow into the local groundwater system, making it
