Science

Bodies of water, including rivers, lakes, reservoirs, streams and creeks play a major role in determining arability and crop yields. Mountains, plateaus, canyons and valleys have been shaped and eroded by water and affected by human activities. Settlers built canals, dug mines, planted crops, removed natural dams, constructed artificial dams and redirected existing waterways. Glen Canyon is one example of a natural feature that has been modified by humans.

This page provides information on Hydrology, Geology, the Environment and a Glossary of geologic, hydrologic and environmental terms. The Utah Geology section provides an expandable, clickable map courtesy of and used with the permission of the Utah Geological Survey.

 
Hydrology

Hydrology is the scientific study of the movement, distribution and management of water on Earth and other planets, including the water cycle, water resources and environmental watershed sustainability.^[1]

Water is one of our most important natural resources. Without water there would be no life on earth. But Earth's water supply is limited and isn't always where humans and other living organisms need it.

Chemical wastes improperly discarded in the past are appearing in today's water supplies. Hydrology knowledge and application help scientists and the public respond to the dynamics of complex water systems and solve water-related problems. Hydrologists play a vital role in finding those solutions.^[1]

In 1878, Powell published Report on the Lands of the Arid Regions of the United States. Most homestead acts granted settlers 160 acres, but Powell thought that if water was limited, that was too much land. He wanted the federal government to use land for other purposes, and wrote about dividing land by its altitude, with high elevation land dedicated to timber, middle land to grazing and low elevation land for farming.^[2]

Powell proposed that western waterways should define state boundaries. But government surveyors in Washington, D.C. decided that straight lines were sufficient for dividing vast western territories. Every state west of a line from North Dakota to Texas has a straight line border, including Wyoming and Colorado, home of the Rocky Mountains.^[2]

Powell died in 1902, the same year the U.S. Bureau of Reclamation was created. For the next 60 years, the bureau planned, supervised and completed construction of western dams at high altitudes and irrigation systems at lower altitudes, as Powell had recommended.^[2]

The dams built by the bureau formed reservoirs. Hoover Dam created 120 mile-long Lake Mead. Glen Canyon Dam created 185-mile-long Lake Powell.

In 1983, University of Arizona Tree Ring researchers warned:

Our results show that the projected climatic change would have serious overall effects on the west. The number of sub-regions that are expected to have water shortages by the year 2000 would essentially double. The regions drained by the Colorado River and the Rio Grande would be especially hard hit as there is presently little, if any, unallocated water in these basins. Allocation changes required to meet a diminishing water supply would be extremely difficult in these basins due to the complex web of international treaties, interstate compacts and both federal and local laws.^[3]

When Lakes Mead and Powell are full, they can hold nearly four years of Colorado River water, but a drought that began in 2000 has caused significant drops in both lakes.^[2]

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Water Properties

More than 70% of Earth's surface is covered by water. Scientists estimate that the hydrosphere. contains about 1.36 billion cubic kilometers of water. The second most common form of the water molecule on our planet is ice. If all of Earth's ice melted, sea-level would rise by about 70 meters.^[1]

Water has several interesting and unique properties:

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Water Phase Changes

The energy required to convert ice into water is called the latent heat of fusion. It takes about 80 calories of heat to convert one gram of ice into water. The energy required to convert water into steam is called the latent heat of evaporation. It takes about 600 calories of heat to convert one gram of water into steam.^[1]

Most of us are familiar with freezing, when liquid water undergoes a phase change and converts to solid ice, and melting, when water also undergoes a phase change from solid ice to liquid water. When heat is added to liquid water it changes to water vapor, dissipating in the atmosphere. When water vapor in the atmosphere cools, it undergoes condendensation.

The two phases we seldom see in daily life are sublimation, when ice converts directly into water vapor in the atmosphere, and deposition, when water vapor converts directly into solid ice. Sublimation can be observed by blowing across the tops of ice cubes in an ice cube tray.

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The hydrologic cycle explains water's motion among oceans, continents, and atmosphere. Water motion is powered by gravity and the Sun.

About 97.5% of Earth's water is contained in the oceans, 2.5% in polar ice caps and ground water, and 0.0001% in the atmosphere.^[1]

A water molecule will stay in the ocean for about 3,000 years before it is evaporated and added back into the water cycle. It will remain in the atmosphere for about 10 days before falling as rain, snow or condensation back into the oceans or onto land. Once on land, water can seep into the ground, flow across the surface and enter streams, rivers, or lakes, or become part of a glacier in colder environments.^[1]

Plants use a lot of water and return it to the atmosphere by transpiration. There is no net water loss in the atmosphere, biosphere, and cryosphere, but overall global distribution changes due to climatic variations and global warming.^[1]

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Water Balance

The simplest form of water balance equation is:

P = Q + E ± ΔS

P = precipitation, Q = runoff, E = evaporation and ΔS = storage in soil, aquifers or reservoirs.^[1]

A water balance analysis has two main applications. It can be used to assess current status and trends in water resource availability in an area over a specific period of time, and strengthen water management decision-making, by assessing and improving the validity of scenarios and strategies.^[1]

Water balance analysis divides water into "green" and "blue" water. "Blue" water, having been used for irrigation, is the surface and groundwater available for irrigation urban and industrial use and environmental flows. "Green" water, from rainfall, is water that has been stored in the soil and that evaporates into the atmosphere.^[1]

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Hydrology Resources

 
Geology

Geology is the study of the Earth's interior and exterior and the processes that shape its mantle, crust and lithosphere. It incorporates thermodynamics, mechanics, chemistry and mathematics.

Geologists study the causes of plate tectonics, earthquakes, volcanoes, rock and mineral formation, mountain building, ocean and river changes, groundwater depletion and pollution, glacier movement and climate change. They evaluate the effects of natural and anthropogenic changes on planet Earth and all of its systems.

John Wesley Powell was a pioneering, self-taught geologist. From his writing, it is obvious that he was aware of geologic principles. Powell identified unconformities, gaps in the geologic record that represent missing time. He was the first geologist to sketch the Great Unconformity in the Grand Canyon.^[1]

Powell's support of single geodetic and topographic systems remain the foundation of federal mapping standards. In 1884 speech to Congress Powell stated, "A Government cannot do any scientific work of more value to the people at large than by causing the construction of proper topographic maps of the country."^[1]

Powell understood that future generations would require accurate and precise mapping systems. His efforts lead to generations eventually led to the nationwide 1:24,000-scale topographic map series used everywhere in the U.S. except Alaska.^[1]

 
Geologic Principles

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Rock Cycle

Common igneous rocks include andesite, basalt, dacite, diorite, dolerite, gabbro, nepheline, obsidian, peridotite, scoria, tuff, and volcanic bombs. ^[4]

Intrusive, or plutonic, igneous rock forms when magma is trapped deep inside the Earth, where it cools slowly over many thousands or millions of years until it solidifies into large blocks or crystals. Intrusive rocks have a coarse grained texture.^[1]

Extrusive, or volcanic, igneous rock forms when magma erupts, becoming lava, and cools near or on Earth's surface. It cools and solidifies quickly when exposed to the lower temperature atmosphere. Its crystals are smaller than those of extrusive rock and those crystals have a very fine-grained or glassy texture. Trapped gas bubbles forming bubbly, vesicular textures.^[1]

Sedimentary rocks form from existing rocks or pieces of once-living organisms deposited in layers on Earth's surface, often in rivers, streams, and lakes. Many southwest mesas and arches are made of sedimentary rock.^[2]

Common sedimentary rocks include breccia, clay, conglomerates, feldspar, limestone, mica, sandstone, and shale. ^[4]

Buried sediments lonse water, and become cemented for form rock. Tuff-like sandstones contain volcanic ash.^[2]

Clastic sedimentary rocks are made up of clasts of pre-existing rocks loosened by weathering, then transported to a river, lake or stream. These rocks may have particles ranging in size from microscopic clay to huge boulders. Their names are based on their clast size. The smallest grains are clay. Silt is slightly larger, followed by sand. Grains larger than 2 millimeters are called pebbles.[2]

Shale is made mostly of clay, siltstone is made up of silt-sized grains, sandstone is made of sand-sized clasts, and conglomerate is made of pebbles surrounded by a matrix of sand or mud.^[2]

The most dominant mineral in sandstone is quartz because it is the most common mineral in the Earth's surface crust.[4]

Biologic sedimentary rocks form when large numbers of living things die and are then compressed. Chert and limestone are types of biologic sedimentary rock.^[2]

Metamorphic rocks are formed from igneous and sedimentary rock subjected to high heat, high pressure, or hot mineral-rich fluids, inside the Earth near tectonic plate boundaries. Metamorphism transforms these rocks into denser rocks consisting of new minerals created by rearrangement of existing mineral components or by reactions with fluids entering the rocks.^[3]

Common metamorphic rocks include amphibolite, eclogite, gneiss, hornfels, marble, migmatite, phyllite, quartzite, schist, serpentinite, and slate. ^[4]

Foliated metamorphic rocks include granite gneiss and biotite schist, which are strongly banded or foliated. Foliation forms when pressure flattens or elongates minerals in a rock into a linear alignment. These rocks develop a platy, sheet-like structure that demonstrates the direction that pressure was applied.^[3]

Non-foliated metamorphic rocks do not have a platy or sheet-like structure because even under high pressure or temperature, it is not possible to change their mineral structures.^[3]

Contact metamorphism occurs when hot igneous rock intrudes into some pre-existing rock baked by the heat, changing the mineral structure of the rock without addition of pressure.^[3]

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One of the earliest estimates of Earth's age was done by William Thompson, also known as Lord Kelvin. In 1862 Kelvin used thermodynamic modeling to estimate Earth's age at between 20 and 400 million years. Kelvin's model disagreed significantly with geologists' estimates, primarily because Kelvin made some incorrect assumptions about Earth's internal cooling rate. In 1869, when Powell began his expedition, English scientist Thomas Huxley challenged Lord Kelvin's calculations. Radioactivity, discovered in 1896, changed science's view of Earth's internal thermodynamics.^[1]

In 1788, James Hutton proposed what would become the foundational principle of geology: uniformitarianism. This principle states that the processes that we see happening on Earth today are the same processes that shaped Earth in the past, and that they will continue into the future. Hutton reasoned that if sand was deposited on a river point bar at a rate of about 2 to 5 centimeters per year, then vast sandstones must also have been deposited at that very slow rate. At the famous unconformity at Siccar Point in Scotland, Hutton said of geologic time that it had "no vestige of a beginning. No prospect of an end."^[1]

The next breakthrough in understanding of geologic time came from English road surveyor William Smith, who was also an amateur paleontologist. He noticed that fossils occurred in distinctive groups and that their order was the same everywhere he identified them. In 1815, Smith developed the law of faunal succession which states that species become extinct, are replaced by new species and that characteristic fossils of a certain age are that age everywhere.^[1]

Major advances were made in geochronology. From the 1820s to the 1850s scientists developed a geologic time scale, published in 1841, based on characteristic fossils. Because a lot of the geologic time scale work was done in England, many geologic period names are derive from English locations.^[1]

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Geology Resources

 
Utah Geology

Environment

 
See the links below for environmental science-related resources, state and federal laws and regulations and environmental programs.

 
Environmental Resources

 
Environmental Laws and Regulations

 
Environmental Programs

 
Glossary

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Denise Meeks, dmeeks@email.arizona.edu