Archive "Water"
What Is a Tornado and How Does One Form?

What Is a Tornado?

A TORNADO IS THE MOST INTENSE type of storm known, expressed as a column of whirling winds racing around a vortex at speeds up to hundreds of kilometers per hour. The May 1999 tornadoes in Oklahoma City, Oklahoma, were estimated to have wind speeds over 500 km/hr. Fortunately, most tornadoes are less than several hundred […]

What Are Some Important Properties of Water?

How Does Water Occur in the Atmosphere?

THE PRESENCE AND ABUNDANCE OF WATER in the atmosphere are a fundamental control of weather and climate, which both have a profound influence on our lives. The molecular structure of water causes it to have special properties that we can observe every day and that are important to life on Earth. In what forms does […]

Living on Million-Year-Old Water

One recent study demonstrated that the Sahara's hidden but increasingly hard-pressed supply of groundwater is actually fossil water that fell as rain more than a million years ago. This source of groundwater fell from the sky when the African continent was farther south, the current Mediterranean Sea was a low-lying desert, and the Sahara was […]

The Ghost of Water

Most of the rugged, sandy terrain of the Sahara drains into expansive internal basins or, in the north, into the ghostly tributaries of the Nile River. A few rivers that arise beyond the limits of the desert drain into it, contributing to its fitful supply of streams and its ancient supply of groundwater. The greatest […]

Canyons and water: a dangerous combo

The lure of a slot canyon – narrow and serene, with walls that ascend far higher than the canyon's width – is hard for a serious hiker to resist Thousands traipse into these flash-flood factories each year unaware of the risk they face. A downpour in one spot can send water pouring into a slot […]

Water, water, everywhere…

Water exists almost everywhere on the Earth. In the oceans it can be thousands of metres deep. But it also occurs in the form of ponds and puddles (which we shall not dwell on too much), seas and lakes, streams and rivers, and ice caps and glaciers, the subject of our next chapter. Water makes […]

The Hydrologic Cycle

Bodies of Water and Landforms

A HUMAN PERSPECTIVE In July 1971, astronaut James Irwin was lifted into space on the Apollo 15 mission. As he circled the earth, he was deeply moved by the beauty of our planet. Later he wrote this: Anyone passing through our solar system would be attracted to the blue planet. They would know that the […]

Surface Water as a Natural Resource

Fresh surface water is a basic natural resource essential to human agricultural and industrial activities. Runoff held in reservoirs behind dams provides water supplies for great urban centers, such as New York City and Los Angeles, as well as irrigation water for agriculture. We can also generate hydroelectric power from surface water where the gradient of a river is steep. […]

River discharge

Surface Water

OVERLAND FLOW AND STREAMFLOW Runoff that flows down the land slopes in broadly distributed sheets is called overland flow. This is different from streamflow, in which the water runs along a narrow channel between banks. Overland flow can take several forms. Where the soil or rock surface is smooth, the flow may be a continuous thin film, called sheet flow. […]

Zones of subsurface water

Ground Water

Water from precipitation can flow through the soil-water belt under the force of gravity. We call this flow percolation. Eventually, the percolating water reaches ground water. Ground water is the part of the subsurface water that fully saturates the pore spaces in bedrock, regolith, or soil (Figure 14.6). The top of the saturated zone is marked by the water table. Above […]

Three states of water

Water in the Environment

In this chapter, we focus on water in the air, both as vapor and as liquid and solid water. Precipitation is the fall of liquid or solid water from the atmosphere that reaches the Earth's land or ocean surface. It forms when moist air is cooled, causing water vapor to form liquid droplets or solid ice particles. If cooling is […]