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Protecting geothermal features

Geothermal features are fragile and easily damaged. Hot springs and

geysers are sensitive to any changes in their underground water supply, andare easily affected by natural events such as earthquakes and landslides.

Over the last 100 years, however, the impact of humans has been vastlygreater than that of natural change.

ENVIRONMENTAL CONCERNS

Although geothermal power was thought to be an environmentally friendly,

renewable resource, by the 1970s there was growing public concern aboutthe irreversible damage to surface features, especially geysers. The situationwas compounded by legal uncertainty about how geothermal development

was regulated and the responsibilities of local and central government.

Conditions must be just right for geysers to occur. Three components must be presentfor geysers to exist: an abundant supply of water, an intense source of heat, and uniqueplumbing. Water is common in nature, heat can come from volcanic activity, but theplumbing is critical. For water to be thrown into the air, geyser plumbing must be water-and pressure-tight.

GEOTHERMAL FEATURES Geothermal refers to the heat coming up from inside the Earth. Volcanoes are a common method by

which this heat escapes through the Earth's crust. When an area of water is involved, and the magma

layer is close to the surface, other geothermal features are also formed. These features occur the world

over. Many of them can be found in Yellowstone Park.

Hot Springs Geothermal features of the earth that involve water occur because the cool water on the surface

permeates down into the Earth. There it is heated to intense levels by rocks that are adjacent to the

magma layer beneath the crust. When this water rises to form a pond of naturally hot water, it is known as

a hot spring. These springs are located around the globe and their temperatures vary depending on how

hot and close the magma layer is beneath the spring.

Mud Pots

Mud pots are formed in the same manner as hot springs. The key difference is that the water that formsa mud pot is more acidic than that of a hot spring. This acidity dissolves the rock as it bubbles out, turning

it to clay and mud. Bubbles spew from the mud pot and land around the outer edges of the pot. This mud

dries and forms a ridge that causes the mud pot to look like a crater blown in the earth.

Geysers A geyser is made from the same water that pools on the Earth's surface to form a hot spring. The

difference here occurs underground. Where hot spring water has a direct route above ground, the water

http://volcano.und.nodak.edu/http://volcano.und.nodak.edu/

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that forms a geyser cannot find its way to the surface. The water is heated beyond the point of boiling as

it snakes its way toward the surface. Once it finally reaches a reservoir near the surface, steam escapes,

which makes room for the water to expand. The pressure builds and eventually the water shoots out as a

geyser.

Fumaroles A fumarole is essentially the Earth's steam vent. Referred to by some as "dry geysers," they occur in

much the same way as a geyser, but the inside of a fumarole contains no liquid water. Water that gets in

a fumarole turns to steam; they are hotter than geysers or springs. When they "erupt," fumaroles send

only water vapor and gases into the air. Fumaroles are sometimes found at the foot of a volcano.

Volcanoes

Volcanoes are the result of the Earth's magma mixing with, and melting rock. This magma isforced toward the Earth's surface in search of a vent through which to escape. When a volcanoerupts, it spews magma, gases, rocks and ash, often violently. Once magma leaves the interior ofthe Earth it is called lava. As lava cools on the volcano's surface and solidifies it builds a gray-black layer of lava rock.effects on the environment

Depletion of resources

The process of extracting geothermal fluids (which include gases, steam and water) for powergeneration typically removes heat from natural reservoirs at over 10 times their rate ofreplenishment. This imbalance may be partially improved by injecting waste fluids back into thegeothermal system.

Damage to natural geothermal features

Natural features such as hot springs, mud pools, sinter terraces, geysers, fumaroles (steam vents) and

steaming ground can be easily, and irreparably, damaged by geothermal development. When the Wairkei

geothermal field was tapped for power generation in 1958, the withdrawal of hot fluids from the

underground reservoir began to cause long-term changes to the famous Geyser Valley, the nearby Waiora

Valley, and the mighty Karapiti blowhole. The ground sagged 3 metres in some places, and hot springs and

geysers began to decline and die as the supply of steaming water from below was depleted.

In Geyser Valley, one of the first features to vanish was the great Wairkei geyser, which used to play to a

height of 42 metres. Subsequently, the famous Champagne Pool, a blue-tinted boiling spring, dwindled away

to a faint wisp of steam. In 1965 the Tourist Hotel Corporation tried to restore it by pumping in some three

million litres of water, but to no avail. Geyser Valley continued to deteriorate, and in 1973 it was shut down

as a tourist spectacle. This story has been repeated many times where there has been geothermal

development.

Subsidence

Extracting geothermal fluids can reduce the pressure in underground reservoirs and cause the land to sink.

The largest subsidence on record is at Wairkei, where the centre of the subsidence bowl is sinking at a rate

of almost half a metre every year. In 2005 the ground was 14 metres lower than it was before the power

station was built. As the ground sinks it also moves sideways and tilts towards the centre. This puts a strain

on bores and pipelines, may damage buildings and roads, and can alter surface drainage patterns.

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Polluting waterways

Geothermal fluids contain elevated levels of arsenic, mercury, lithium and boron because of the underground

contact between hot fluids and rocks. If waste is released into rivers or lakes instead of being injected into

the geothermal field, these pollutants can damage aquatic life and make the water unsafe for drinking or

irrigation.

A serious environmental effect of the geothermal industry is arsenic pollution. Levels of arsenic in the

Waikato River almost always exceed the World Health Organisation standard for drinking water of 0.01 parts

per million. Most of the arsenic comes from geothermal waste water discharged from the Wairkei power

station. Natural features such as hot springs are also a source of arsenic, but it tends to be removed from

the water as colourful mineral precipitates like bright red realgar and yellowy green orpiment.