Question 11;
The answer is D. Infiltration means that the rainwater, after falling to the ground, seeps and percolates into the ground and fills the spaces in the permeable rocks. Some of the seeped water remains in the soil subsurface while the other water seeps deep into the ground and fills or replaces water in aquifers.
Question 12;
The answer is C. Surface runoff occurs when rainwater accumulates on the ground more than it can percolate into the ground. Th water then flows on the surface by gravity. Surface runoff causes soil erosion especially when the soil is not covered by vegetation. Surface runoff is severe on impervious rocks such as on tarmac and concrete in an urban center.
Question 13;
The answer is D. Soil (a major component of the pedosphere) is the topmost layers of the earth's crust where vegetation grows. The layer is composed of weathered rock and organic matter from dead living organisms. The soil is also teeming with organic life that is involved in nutrient cycles that support plant growth.
Question 14;
The answer is D. Limestone is mainly composed of Calcium Carbonate mineral. It is easily dissolved by acid in a chemical process. When rainwater falls it is slightly acidic due to the dissolving of atmospheric carbon dioxide to form carbonic acid. This may also be exacerbated by the presence of other gases in the air such as sulfur dioxide after a volcanic activity. Over many years of rainfall and slow but progressive dissolution of the limestone, a cave is formed in the ground. Stalactite and Stalagmite are speleothems formed in the cave.
Question 15;
The answer is C. The flood stage is the phase at which the river is considered to be breaking its banks as the water level goes above its highest banks. Communities at the lower stages of the river are the most affected by flooding when a river reaches flood stage. A tide gauge is used to determine the stages of flooding of a river.
Question 16;
The answer is D. Humus (of well refined dead organic matter) is what gives soil is a dark color because it is dark colored itself, hence intuitively, dark-colored soils have the most organic matter. It is this humus that enables the soil to hold water and nutrients hence significant in plant growth.
Question 17;
The answer is C. An example of chemical weathering is the limestone weathering as explained in question 14. warm, damp climates are best for chemical weathering because they are best for conditions for chemical reactions. Other by dissolution, other methods of chemical weathering of rick is by oxidation (especially rocks with iron mineral content), and hydrolysis.
Question 18;
The answer is A. This is the land between two adjacent valleys. There are 3 types of divides. A minor divide in which the two drainage rivers meet at a particular point before draining to the ocean or lake. A major divide is where the two river drainages never meet. A continental divide occur=s when the two drainage rivers flow into different oceans.
Question 19;
The answer is A. Radon gas is formed from the natural decay of radioactive elements such as uranium and thorium. They are found in small quantities in the underground and the gas is odorless and colorless hence easily undetectable. It is harmful in high concentrations especially when released as residues from the oil and gas industry.
Question 20;
The answer is D. Just as the common saying goes, <em>water is life</em>, so it goes without saying that life cannot be sustained without fresh water. This is because water is a significant requirement for basic life processes such as photosynthesis and cellular respiration.
