There are four types of geothermal 
deposits, but only one is used 
commercially: Hydrothermal Fluid 
Reservoirs

Hydrothermal Fluid Reservoirs: 
areas of the crust where hot rock 
occurs at relatively shallow depths 
and natural groundwater is heated 
to extremely high temperatures.

These reservoirs may take form on the surface of earth as hot springs or geysers.

High temperature hydrothermal deposits are mainly used to run electricity producing 
power plants.

Low temperature deposits are mainly used to heat buildings.

Volcanoes can be utilized as a source of energy.  A pipe can be inserted into the 
magma and water circulated throughout the pipe as it is heated up.

Pipes may melt, but progress has continuously been made in finding a solution to 
this problem.

In the future, geothermal power may be produced from developing technology in 
the field of hot dry rock use.  Wells are created after drilling into these hot dry 
rocks (2 to 6 miles beneath the earth's surface).  The rock between these two 
wells is fractured and cold water is pumped down one well and up the other after 
being heated by the hot rock in between.  This water (now extremely hot) is used 
to create electricity.  No commercial plants using this method have been created 
using this method, but this is a very feasible idea

Geothermal energy is created using and harnessing heat, which is primarily 
generated by radioactive decay within the earth.  

This heat reaches the surface of the earth by various ways including molten rock, 
erupting volcanoes, and hot geysers and springs.

Electricity is created by utilizing naturally vented steam directly or by heating 
water to produce steam to drive a turbine generator.

Geothermal energy constitutes .2% of the primary energy consumed in the U.S.

Geothermal energy use is predicted to expand vastly in the future.

Geothermal energy can be used directly as a heating source or it can be used to 
produce electricity.  

Iceland, lying along the mid-ocean ridge, heats 80% of its buildings using 
geothermal heated water.

Hawaii is well suited for the use of geothermal energy.

Geothermal energy is an undepleatable resource in a sense in most methods on 
a human timescale, because the earth is not going to cool down any time soon.  

Not practical everywhere; most easily utilized along plate margins and at other 
points where hot magma comes close to the surface.

Once a deposit is tapped, such as a geopressured brine (which is a deposit of 
hot salty water under pressure sometimes containing dissolved gases such as 
methane), it can not be renewed in a human time frame much like fossil fuels.

Although considered to be environmentally safe and clean, geothermal energy 
production still creates some environmental hazards.

The process of production expels excessive quantities of heat into the  
environment causing thermal pollution which disrupts the natural ecosystem.

Some of the hot water pumped up from underground in geothermal production 
processes contains dissolved salts, minerals, and heavy metal which may be 
toxic on the earth's surface.

Geothermal operations require large quantities of water as cooling and 
condensing agents, and as transporters of heat.