Air is then breathed into the windpipe and lungs, while the mucus is swallowed (figure 3). Other. Other interesting structures associated with the nasal and sinus tract: Tear duct (called the nasolacrimal duct): drains tears from the inside corner of the eye into the nasal cavity (figure 1).
Human activity is the main cause of soil degradation. Agriculture plays a large part in soil degradation, especially clearing, irrigation, the spreading of chemical fertilizer â¦ s and pesticides, overgrazing and even the passage of heavy farming equipment. Tillage and the clearing and deforestation of large plots of land also lead to soil degradation.
But erosion can be speeded up by such human activities as farming and mining. Erosion begins with a process called weathering; in this process, environmental factors break rock and soil into smaller pieces, and loosen them from the earth's surface. When the wind whips up a dust storm that stings our eyes, its ability to move sand is very clear. But the most powerful erosive force on the earth is not wind but water, which causes erosion in its solid form of ice and as a liquid. Water in its liquid form causes erosion in many ways. Streams from tiny creeks to huge rivers carry tons of eroded soil and rocks every year.