Tag: study of continents - north america

Barkan is a crescent-shaped sand dune produced by the action of wind predominately from one direction. One of the commonest types of dunes, it occurs in sandy deserts all over the world.

Wind erosion has the greatest impact on areas with dry soil because it is easier for wind to pick up and transport dry, light soil. Characteristically, deserts have dry soil, or sand, that is easy to transport. Also, deserts often have fewer physical barriers, such as hills, trees, or other structures, that can slow the wind movement.

Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind, water, or ice.

An oxbow is a crescent-shaped lake lying alongside a winding river. The oxbow lake is created over time as erosion and deposition of soil change the river's course.

Moraines are ridge-like depositional features of glacial tills. They are long but narrow ridge with height more 30 meters. Moraines are consist of rock materials of heterogeneous shapes and size.

Sea beaches are not the erosional feature of sea waves. They are formed due to the depositional activities of sea waves.

The seasons are caused by the tilt of the Earth's rotational axis away or toward the sun as it travels through its year-long path around the sun.

Latitude is a measure of the distance you are located from the equator.  It is commonly shown as an imaginary horizontal line that goes across the earth on maps and is used along with longitude as a reference point to determine location. The tilt of the earth affects the seasons we experience throughout the year.

The earth moves around the sun in an elliptical fashion, and one complete orbit around the sun take one year. An interesting fact is that it is not the proximity of the earth to the sun that determines the season; we are actually closest to the sun in January, not July.  Instead, the tilt of the earth is the key. When the Northern Hemisphere is tilted towards the sun, the Southern Hemisphere is tilted away from the sun. This leads to summer in the Northern Hemisphere and winter in the Southern Hemisphere as the Northern Hemisphere experiences the most direct sunlight and solar heating.

Temperature decreases with an increase in altitude. The reason or this is:

The ground absorbs more radiation from the sun and during night time the ground emits this absorbed radiation to its surroundings. The molecules of air surrounding the land also absorb the emitted radiation from the ground. At locations near sea level where air is most dense the air is very warm at sunset and a few hours after sunset.

At higher altitudes, the air get very rarified i.e. less dense. The less-dense air can seldom absorb the heat emitted by the ground because they are very far apart. The net result is a drop in temperature at higher altitudes.

As a summary, the decrease in temperature is due to the very less heat energy absorbed by the air molecules and the very far distance of air molecules from each other.

C. The tilt of Earths Axis

Seasons happen because Earth's axis is tilted at an angle of about 23.4 degrees and different parts of Earth receive more solar energy than others. Because of Earth's axial tilt, different areas of Earth point toward or away from the Sun at different times of the year. Around the June solstice, the North Pole is tilted toward the Sun and the Northern Hemisphere gets more of the Sun's direct rays. This is why June, July and August are summer months in the Northern Hemisphere. At the same time, the Southern Hemisphere points away from the Sun, creating winter during the months of June, July and August. Summer in the Southern Hemisphere is in December, January, and February, when the South Pole is tilted toward the Sun and the Northern Hemisphere is tilted away.