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The Sahel is the ecoclimatic and biogeographic zone of transition in Africa between the Sahara to the north and the Sudanian Savanna to the south. Having a semi-arid climate, it stretches across the south-central latitudes of Northern Africa between the Atlantic Ocean and the Red Sea. Wikipedia
Area: 1.179 million mi²
The Sahel has a tropical, hot steppe climate (Köppen climate classification BSh). The climate is typically hot, sunny, dry and somewhat windy all year long. The Sahel's climate is similar to, but less extreme than, the climate of the Sahara desert located just to the north.
Explanation:
The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken up into tectonic plates. The Earth's lithosphere is composed of seven or eight major plates (depending on how they are defined) and many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The relative movement of the plates typically ranges from zero to 100 mm annually.[2]
Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the lithosphere remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle. Earlier theories, since disproven, proposed gradual shrinking (contraction) or gradual expansion of the globe.[3]
Tectonic plates are able to move because the Earth's lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by tidal forces of the Sun and Moon. The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.
Answer: D) None of the above
Explanation: The subschema differs from the schema in that one denotes the appearance of data in the Database Base Management System (DBMS) while the subschema which is also referred to as the external schema is that subset of the schema is visible or relevant to the user. Thus, It is the view of the database which is visible to an application program. Virtual tables in a database usually represents an object structures like a table which is the result of running certain database commands or functions such as the create table, view, select and so on. Virtual tables are not stored directly in database files.
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Explanation: Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the components of pollution, can be either foreign substances/energies or naturally occurring contaminants.
Answer: Weather can change from minute-to-minute, hour-to-hour, day-to-day, and season-to-season. Climate, is the average of weather over time and space.
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