Hydrosphere

A hydrosphere (from Greek - hydor, "water" and - sphaira, "sphere") in physical geography describes the combined mass of water found on, under, and over the surface of a planet.

The total mass of the Earth's hydrosphere is about 1.4 × 1018 tonnes, which is about 0.023% of the Earth's total mass. About 20 × 1012 tonnes of this is in the Earth's atmosphere (the volume of one tonne of water is approximately 1 cubic metre). Approximately 75% of the Earth's surface, an area of some 361 million square kilometres (139.5 million square miles), is covered by ocean. The average salinity of the Earth's oceans is about 35 grams of salt per kilogram of sea water (35 ‰).

Other hydrosphere

A thick hydrosphere is thought to exist around the Jovian moon Europa. The outer layer of this hydrosphere is almost entirely ice, but current models predict that there is an ocean up to 100 km in depth underneath the ice. This ocean remains in a liquid form because of tidal flexing of the moon in its orbit around Jupiter. The volume of Europa's hydrosphere is 3 × 1018 m3, 2.3 times that of Earth.

It has been suggested that the Jovian moon Ganymede and the Saturnian moon Enceladus may also possess sub-surface oceans. However the ice covering is expected to be thicker on Jupiter's Ganymede than on Europa.

Hydrological cycle

Insolation, or energy (in the form of heat and light) from the sun, provides the energy necessary to cause evaporation from all wet surfaces including oceans, rivers, lakes, soil and the leaves of plants. Water vapor is further released as transpiration from vegetation and from humans and other animals.

Aquifer drawdown or over drafting and the pumping of fossil water increases the total amount of water in the hydrosphere that is subject to transpiration and evaporation thereby causing accretion in water vapor and cloud cover which are the primary absorbers of infrared radiation in the earth's atmosphere. Adding water to the system has a forcing effect on the whole earth system, an accurate estimate of which hydrogeological fact is yet to be quantified.

What is the HYDROSPHERE?

The hydrosphere is the liquid water component of the Earth. It includes the oceans, seas, lakes, ponds, rivers and streams. The hydrosphere covers about 70% of the surface of the Earth and is the home for many plants and animals.

Hydrosphere

The hydrosphere, like the atmosphere, is always in motion. The motion of rivers and streams can be easily seen, while the motion of the water within lakes and ponds is less obvious. Some of the motion of the oceans and seas can be easily seen while the large scale motions that move water great distances such as between the tropics and poles or between continents are more difficult to see. These types of motions are in the form of currents that move the warm waters in the tropics toward the poles, and colder water from the polar regions toward the tropics. These currents exist on the surface of the ocean and at great depths in the ocean (up to about 4km).

Hydrosphere

The characteristics of the ocean which affects its motion are its temperature and salinity. Warm water is less dense or lighter and therefore tends to move up toward the surface, while colder water is more dense or heavier and therefore tends to sink toward the bottom. Salty water is also more dense or heavier and thus tends to sink, while fresh or less salty water is less dense or lighter and thus tends to rise toward the surface. The combination of the water's temperature and salinity determines whether it rises to the surface, sinks to the bottom or stays at some intermediate depth.

History of Hydrosphere

1. Formation

There are several theories regarding the formation of the Earth's hydrosphere. This planet contains proportionately more surface water than comparable bodies in the inner solar system. Out gassing of water from the Earth's interior is not sufficient to explain the quantity of water.

One hypothesis that has gained popularity among scientists is that the early Earth was subjected to a period of bombardment by comets and water-rich asteroids. Much of the water on the surface today is thought to have originated from the outer parts of the solar system, such as from objects that arrived from beyond Neptune.

2. Ice ages

During the history of Earth, there have been a series of periods in which a significant portion of the hydrosphere was locked up in the form of glacial ice. It has even been hypothesized that during the Cryogenian period, this sea ice extended all the way to the equator (see Snowball Earth).

It is currently believed that four major ice ages have taken place during our planet's history. The current ice age began about 4 × 107 years ago, and gained in intensity during the Pleistocene. The most recent withdrawal of ice sheets occurred only 10,000 years ago.

3. Life

All currently recognized forms of life rely on an active hydrosphere. All organic chemistry indicative of life occurs with water as its solvent. The water cycle in the Earth's hydrosphere allows for the purification of salt water into freshwater. The action of both evaporation and wetland swamps serves to remove a large portion of atmospheric pollutants from the atmosphere (i.e. acid rain). Through this process, the water cycle purifies the gaseous atmosphere. Although most life on the planet exists in the saltwater oceans, humans are particularly interested in the hydrosphere because it provides the fresh water we depend upon.

The search for life on other celestial bodies in our solar system is focused on first locating water. The hydrospheres of other planetary bodies are also the focus of research, to find places that humans can inhabit without having to transport all their water with them.

4. Extinction

Scientists estimate that in approximately 5 × 109 years, the Sun will have exhausted the supply of hydrogen in its core and will evolve into a supergiant. The outer atmosphere will expand significantly, and planet Earth will lie within the Sun's photosphere (the part of the Sun that is not transparent to light). During this process, the surface temperature will rise well above the boiling point of water, and all water on the Earth's surface will evaporate.

Water cycle

The water cycle, also known as the hydrologic cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Water can change states among liquid, vapour, and ice at various places in the water cycle. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go, in and out of the atmosphere. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid, and gas.

The hydrologic cycle also involves the exchange of heat energy, which leads to temperature changes. For instance, in the process of evaporation, water takes up energy from the surroundings and cools the environment. Conversely, in the process of condensation, water releases energy to its surroundings, warming the environment.

The water cycle

Water pollution

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans and groundwater). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds.

Water pollution affects plants and organisms living in these bodies of water; and, in almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities.

Water pollution

Introduction

Water pollution is a major global problem. It has been suggested that it is the leading worldwide cause of deaths and diseases,and that it accounts for the deaths of more than 14,000 people daily.An estimated 700 million Indians have no access to a proper toilet, and 1,000 Indian children die of diarrheal sickness every day. Some 90% of China's cities suffer from some degree of water pollution, and nearly 500 million people lack access to safe drinking water.n addition to the acute problems of water pollution in developing countries, industrialized countries continue to struggle with pollution problems as well. In the most recent national report on water quality in the United States, 45 percent of assessed stream miles, 47 percent of assessed lake acres, and 32 percent of assessed bay and estuarine square miles were classified as polluted.

Groundwater pollution

Interactions between groundwater and surface water are complex. Consequently, groundwater pollution, sometimes referred to as groundwater contamination, is not as easily classified as surface water pollution. By its very nature, groundwater aquifers are susceptible to contamination from sources that may not directly affect surface water bodies, and the distinction of point vs. non-point source may be irrelevant. A spill or ongoing releases of chemical or radionuclide contaminants into soil (located away from a surface water body) may not create point source or non-point source pollution, but can contaminate the aquifer below, defined as a toxin plume. The movement of the plume, called a plume front, may be analyzed through a hydrological transport model or groundwater model. Analysis of groundwater contamination may focus on the soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants.

Causes

The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining what is a natural component of water, and what is a contaminant. High concentrations of naturally-occurring substances can have negative impacts on aquatic flora and fauna.

Oxygen-depleting substances may be natural materials, such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.

Thermal pollution

Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Elevated water temperatures decreases oxygen levels (which can kill fish) and affects ecosystem composition, such as invasion by new thermophilic species. Urban runoff may also elevate temperature in surface waters.

Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.

Flood

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.

Picture of flooding area

Principal types and causes

Riverine Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding

the capacity of a river's channel. Causes include heavy rains from monsoons, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack. Unexpected drainage obstructions such as landslides, ice, or debris can cause slow flooding upstream of the obstruction.

Fast kinds: include flash floods resulting from convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier.

Estuarine Commonly caused by a combination of sea tidal surges caused by storm-

force winds. A [storm surge], from either a tropical cyclone or an extra tropical cyclone, falls within this category.

Coastal Caused by severe sea storms, or as a result of another hazard (e.g.

tsunami or hurricane). A storm surge, from either a tropical cyclone or an extra tropical cyclone, falls within this category.

PRESENTATION IN

NAT SCI

Prepare by: ROSALINDA B. ESQUIVEL

AB English language II-A

Submitted to:Ms. MA. KATRINA

POBRE