Physical Geography

It is the study of characteristic features of the lithosphere, atmosphere, hydrosphere, biosphere, and environment.

Umbrella Species

Umbrella species are such kind of species whose conservation indirectly protects many other species in the ecosystem. Hence, umbrella species can be used to make conservation-related decisions. These species have a larger habitat needs and other requirements. Furthermore, when umbrella species are conserved, it will result in the conservation of many other species. Hence, monitoring …

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Igneous Rocks

Igneous rocks are formed when molten material, or magma, solidifies. The magma moves upward from pockets a few kilometers below the Earth’s surface, through fractures in older solid rock. There the magma cools, forming rocks of mineral crystals. Most igneous rock consists of silicate minerals— chemical compounds that contain silicon and oxygen atoms. These rocks also contain mostly metallic elements. The mineral grains in igneous …

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Metamorphic Rocks

The mountain-building processes of the Earth’s crust involve tremendous pressures and high temperatures. These extreme conditions alter igneous or sedimentary rocks, transforming them into metamorphic rocks. In many cases, the mineral components of the parent rock are changed into different mineral varieties. In some cases, the original minerals may recrystallize. Extreme heat and pressure transform shale into slate …

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Jet Streams

Jet streams are wind streams that reach great speeds in narrow zones at a high altitude. They occur where atmospheric pressure gradients are strong. Along a jet stream, the air moves in pulses along broadly curving tracks. The greatest wind speeds occur in the center of the jet stream, with velocities decreasing away from it. …

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Ecological Succession

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 …

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Fault

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 …

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Thunderstorm

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 …

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Earthflow

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 …

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Stratovolcano

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 …

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Composition of the Atmosphere

The Earth is surrounded by air—a mixture of various gases that reaches up to a height of many kilometers. This envelope of air makes up our atmosphere. It is held in place by the Earth’s gravity. Almost all the atmosphere (97 percent) lies within 30 km of the Earth’s surface. The upper limit of the …

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