Crater Lakes and Salines Lakes

Crater lakes are formed by the impounding of water in the craters of extince volcanoes. These lakes have a circular outline and are surrounded by deep walls of lava. Usually Crater Lakes are very deep and their depth is the greatest near the centre. The Crater Lake of Oregon and the Caldera of Roman Campagana are some of the most outstanding lakes of this type. Such lakes are also found in the Avergne District of France and the Eifle region of Germany.
Salines lakes are the salt water lakes of arid and desert regions. These are not so short-lived as the playas and are more permanent. They have a more constant water supply but are bitter in taste because of the lack of an outlet. But these may also disappear leaving behind a ‘salt-Pan’. The best case in point is the 4000 square miles saline Lake Eyre, which lies in the ‘Dead Heart’ of Australia.

Coulee lakes and Sink Lakes

Coulee lakes are also of volcanic origin but they are formed by the flow of lava across the valley of some river so that it blocks the river flow and gives rise to lakes. Lake Tana of Absyssinia is a characteristic example. Several lakes of this type are found in Iceland. Such lakes are usually rectangular in outline but may be irregular also. Sink lakes are characteristic of limestone regions, where the water descending through the shallow holes produces large underground caves. In case of roof of such a subterranean cavern collapses, a basin is formed. Such a basin resembles a sink and has also been formed by the sinking of the land. The lakes formed in these depressions are known as ‘Sink Lakes’. These are usually small in size.

Wonder River Amazon


The greatest river of South America, the Amazon is also the world’s largest river in water volume and the area of its drainage basin. Together with its tributaries the river drains an area of 2,722,000 square miles (7,050,000 square kilometers)—roughly one third of the continent. It empties into the Atlantic Ocean at a rate of about 58 billion gallons (220,000 cubic meters) per second.

The Amazon varies in width from 4 to 6 miles (6 to 10 kilometers); its mouth is more than 150 miles (240 kilometers) wide. The largest oceangoing steamers can ascend the river 1,000 miles to Manaus, a Brazilian inland port.
For most of its course the river flows just south of the Equator, and so the Amazonian climate is hot and humid. Annual rainfall amounts to about 50 inches (130 centimeters), while the average temperature over a year is about 85° F (30° C). Most of the Amazon Basin is a lowland forest of hardwoods and palms. The northeastern portion has extensive savannas, or grasslands, with occasional trees and shrubs.

Plants and Animals

The remarkably rich and diverse Amazon Basin plant and animal life is a resource of world importance. Of all the species of plants in the world, almost three fourths, many of which are still unidentified, live in the Amazon Basin. The Amazon has often been described as a vast sea of fresh water that supports about 1,500 to 2,000 species of fish, including catfish, electric eels, and piranhas. The basin also has an immense variety of insect, bird, reptile, and mammal life.

The vegetation of the Amazon jungle grows rapidly, soon covering cleared areas unless it is cut back constantly. Again and again the jungle has defeated settlement efforts. At the same time, conservationists are concerned about the overcutting of valuable plants such as hardwood trees and also the destruction of rare plant species when the jungle is burned over for clearing. The many Amazonian plants are a valuable source for development of new hybrids.

Mammals include the capybara, a rodent weighing up to 110 pounds (50 kilograms) whose flesh is eaten; the tapir, an edible kind of pig; the nutria, a tropical otter whose pelt is traded; the great anteater; and many kinds of monkeys. Markets along the river sell a variety of fish, including the pirarucu, which weighs up to 325 pounds (150 kilograms), and the giant catfish. Silver carp, neon tetras, and the flesh-eating piranhas are shipped to tropical fish stores throughout the world. The electric eel is a dangerous fish capable of discharging up to 500 volts.

The wide range of vividly colored Amazonian birds includes hummingbirds, toucans, and parrots. Among the reptiles are the anaconda, a huge snake that crushes its victims; the poisonous coral snake; and alligators. Giant butterflies are among the most spectacular of the insects.

Essential Terms Associated With Ice

Ice is the solid form of water, formed by freezing, the compaction of snow and the condensation of water vapour directly into crystals. The density of the ice is 0.9166, that is less than water, and thus Ice floats.
Ice Age- A geological period of widespread glacial activity, when Ice sheets covered large parts of the continents is called Ice Age.
Ice Barrier- The edge of the Ancient ice sheet is called ice barrier, for example, the Ross Ice Barrier.
Ice Blink- The glare from the underside of a cloud layer, produced by the reflection from an ice surface below, as in the case of an ice sheet or of pack ice, is called ice blink. This may produce eye irritation and even snow blindness.
Ice Cap- A permanent mass of ice covering plateaus and high latitude islands, but smaller than an ice sheet; for example Spitsbergen; Novaya Zemlya; Franz Josef Land
Ice Dam- A dam on river caused by clocks of ice, which may result in widespread flooding in spring and early summer, is called ice dam, as along the Siberian and Canadian rivers (also called Ice Jam)
Ice Edge-The boundary between open water and a mass of floating sea ice.
Ice- Field- The term refers to a large continuous area of Packice or sea ice by both USA and Britain definition. Generally it is used much more widely; for example, the Columbia Ice field in Jasper National Park, Alberta, Canada which is 130 square miles in area.
Ice Fall- A confused labyrinth of deep clefts and ice pinnacles formed by the intersection of ‘crevasses’ where a glacier steepens, is called Ice fall, for example, the glaciers moving down from the flanks of Mont Blank to the Chamonix valley, descending over 6000 feet in only 2 miles. The huge Khumbu ice fall was a major obstacle in the approach of dimbers to the South Col. Of Everest.
Ice Floe- a thin, detached, floating horizontal sheet of sea ice is called Floe; hence Ice Floe.
Ice Fog- A fog consisting of minute ice crystals suspended in the air, in conditions of calm air and low temperatures, is called Ice fog.
Ice Front- A cliff of ice, the seaward face of a floating mass of ice, such as an ice shelf or tidal glacier, is called an Ice Front.
Ice Jam- A mass of broken ice fragments, especially during spring melting jammed in a narrow channel, causing flooding is called Ice Jam.
Icelandic Low- The mean sub polar atmospheric low pressure area in the North Atlantic Ocean between Iceland and Greenland, most marked in winter, it is not a very intense, stationary ‘low’, but an area of rapidly moving individual ‘lows’, interrupted by occasional periods of higher pressure.
Ice Shelf-A large floating ice sheet attached to the coastline is called an Ice Shelf for example, the Ross Ice Shelf.

Biosphere Reserve

Biosphere reserves are ‘areas of terrestrial and coastal/ marine ecosystems or a combination thereof, which are internationally recognised within the framework of UNESCO’s Programme on Man and the Biosphere (MAB)’. 

Reserves are nominated by national government; each reserve must meet a minimal set of criteria and adhere to a minimal set of conditions before being admitted to a  before being admitted to a network. 

Each biosphere reserve is intended to fulfil three complementary functions: a conservation function, to preserve genetic resources, species, ecosystems and landscapes; a development function, to foster sustainable economic and human development, and a logistic support function, to support demonstration projects, environmental education and training, and research and monitoring related to local, national and global issues of conservation and sustainable development.

Essential Terms Associated With Snow

The type of precipitation formed when water vapour condenses at a temperature below freezing point, so passing directly from the gaseous to the solid stage, and forming minute spicules of ice. These unite into crystals which are either ‘flat hexagonal plates’ or ‘hexagonal prisms’, revealing infinite variations in their patterns. These crystals aggregate into Snow Flakes, where the lower atmosphere is sufficiently cool, they will reach the ground without melting. Snow may be dry and powdery under low temperature conditions, as in Antarctica.
Snow Avalanche- A fall of snow down a hill side is called Snow Avalanche. It may be-
1.      Wind Slab- where the snow is crusted and compacted.
2.      A dry Snow Avalanche- usually of new snow in winter and
3.      A Wet Snow Avalanche- caused by a sudden spring thaw.
Snow Drift- A bank of snow drifted by the wind which has accumulated against obstacles, sometimes to great depths; this may block roads and railway lines, unless protected by barriers, sheds or snow drift fences.
Snow Field- An area of permanent snow which has accumulated in a basin shaped hollow among the mountains or on a plateau; for example, the Ewig Schneefeld near the Jungrau in the Bernese Oberland.
Snow Line- The lowest edge of a more or less continuous snow cover is called a snow line.
The Permanent Snow Line- is the level at which wastage of snow by melting in summer fails to remove winter accumulation. This varies with latitude, altitude and aspect. At the poles it lies at sea level, in south Greenland at 2000 feet, in Norway at 4 to 5000 feet, in the Alps about 9000 feet, in Eastern Africa at 16000 feet.
The Winter Snow Line-fluctuates from year to year, but is markedly lower than the permanent snowline. There is no permanent snow line in Great Britain, though in winter in the Highlands of Scotland snowline lies above 3000 feet for about 80 days.

What are Springs?

A place where water naturally flows to the surface is called a Spring. Springs differ between themselves by the conditions of natural underground water discharge depending on such factors as the nature of the water- bearing rocks (porous or fractured), the exposure of the river or gulley slope, the mode of occurrence of the rocks etc. Sometimes, springs emerge at the sea floor and are called ‘Submarine Springs’. 

Springs fed by ground waters are called Gravity Springs, and htose fed by pressure waters are called Ascension Springs. Springs fed by vadose water are subjected to the greatest fluctuations, to the point of complete disappearance at certain times. Most constant are gravity springs fed by ground waters, even though their flow and properties also vary depending upon seasonal changes in the hydrometeorological conditions.
Ascension springs are the natural places of discharge of pressure waters. Typically they are distinguished by more or less constant regime, i.e. head of pressure, flow, chemical composition, temperature etc. they are usually confined to the discharge areas of artesian basins and are often associated with tectonic fault zones.
A springthat breaks out at or near the foot of an escarpment, especially where chalks lie on clay or limestone and sand stone lie on clay.
Vauclusian Spring- the resurgence of reappearance of an underground stream, called after the Fontaine de vaucluse in the lower Rhone valley. It occurs commonly in the limestone country, where water wears subterranean ramifications, finally issuing from the limestone at its base.

What is Volcano?

On the basis of frequency of eruption, there are active, dormant and extinct or ancient volcanoes. The volcanoes which erupt fairly frequently as compared to others are active. Only a few volcanoes remain more or less continually in eruption for a long period, but intermittent activity is more common. The dormant (from Latin word dormer, meaning, ‘to sleep’) volcanoes are those in which eruption has not occurred regularly recently.

These volcanoes undergo long intervals of repose during which all external signs of activity cease. Those volcanoes in which no eruption has been recorded in historic times are said to be extinct. Before a volcano becomes extinct, it passes through a waning stage during which steam and other hot gases and vapors are exhaled. These are known as fumaroles or solfataras.

Sometimes, a volcano thought to have become dormant suddenly becomes active. The Barren Island in an Andaman and Nicobar Islands of India is an example.

There are no volcanoes in the Himalayan region or in the Indian peninsula. Barren island, lying 135 km north-east of Port Blair, was thought to be dormant since it last erupted in early nineteenth century. It suddenly became active again in March 1991.

A second phase of eruption started in January 1995. The island has its base 2,000 m below sea level and its crater is about 350 m above the level of the sea. After its activity in the nineteenth century, it passed though a mild solfataric stage as evidenced by the sublimations of sulphur on the walls of the crater. The other volcanic island in Indian Territory is Narcondam, about 150 km north-east of barren island; it is probably extinct. Its crater wall has been completely destroyed.