Wave-like bands are formed in the crustal rocks due to tangential compressive force resulting from horizontal movement caused by the endogenetic force originating deep within the earth. Such bands are called ‘Folds’ wherein some parts are bent up and some parts are bent down. Different Components of a Fold: The up folded rock strata in the …
Plant and animal communities change through time. Walk through the country and you’ll see patches of vegetation in many stages of development—from open, cultivated fields through grassy shrublands to forests. Clear lakes gradually fill with sediment and become bogs. We call these changes—in which biotic communities succeed one another on the way to a stable …
Faults are the fractured surface in the Earth’s crust. During the formation of a fault, the vertical displacement of a rock block may occur up to several 100 meters and horizontally the rock blocks may be displaced up to several kilometers. A fault represents weaker zones of the earth where crustal movements become operative for a longer …
A thunderstorm is any storm that produces thunder and lightning. At the same time, thunderstorms can also produce high winds, hail, and tornadoes. They are typically associated with cumulus clouds that indicate the presence of rising, unstable air. It is this rising motion that produces the characteristic rainfall and lightning that accompany thunderstorms. Thunderstorms can …
Drainage system refers to the origin and development of streams through time. The examples of drainage systems are consequent, subsequent, and antecedent and superimposed streams, etc. The origin and subsequent evolution of any drainage system in a region are determined and controlled by two main factors: The nature of the initial surface and slope and …
The troposphere is the lowest atmospheric layer. All human activity takes place here. Everyday weather phenomena, such as clouds and storms, mainly happen in the troposphere. Here temperature decreases with increasing elevation. The troposphere is thickest in the equatorial and tropical regions, where it stretches from sea level to about 16 km. It thins toward the …
The coast is the shore of sea or ocean. When we use the word ‘coasts’ or ‘coastlines’, we’re referring to the zone in which coastal processes operate, or have a strong influence. The coastline includes the shallow water zone in which waves perform their work as well as beaches and cliffs shaped by waves. Types of …
In humid climates, water-saturated soil, regolith, or weak shale can move down a steep slope in just a few hours. This is an earthflow. It’s common to see shallow earthflows, affecting only the soil and regolith, on sod-covered and forested slopes that have been saturated by heavy rains. An earthflow can affect a few square …
In contrast to the thick, gassy felsic lava that forms stratovolcanoes, mafic lava (basalt) is not very viscous and holds little gas. Eruptions of basaltic lava are usually quiet, and the lava travels long distances to spread out in thin layers. Typically, then, large basaltic volcanoes are broadly rounded domes with gentle slopes. They are …
Felsic lavas (rhyolite and andesite) are very thick and gummy, resisting flow. So, felsic lava doesn’t usually flow very far from the volcano’s event, building up steep slopes. When the volcano erupts, ejected particles of different sizes, known collectively as tephra, fall on the area surrounding the crater, creating a cone shape. The sluggish streams of felsic …