8th Grade Trivia Facts On Earth Science! Quiz

1. Where do most nutrients in soils come from?

Broken down rocks

Decaying organic matter

Rain fall

Volcanic eruptions

Most nutrients in soils come from decaying organic matter. When plants and animals die, their remains decompose and break down into organic matter. This organic matter releases essential nutrients such as nitrogen, phosphorus, and potassium into the soil. These nutrients are then absorbed by plants and used for their growth and development. Over time, the accumulation of decaying organic matter enriches the soil and provides a fertile environment for plants to thrive.

Explanation

Most nutrients in soils come from decaying organic matter. When plants and animals die, their remains decompose and break down into organic matter. This organic matter releases essential nutrients such as nitrogen, phosphorus, and potassium into the soil. These nutrients are then absorbed by plants and used for their growth and development. Over time, the accumulation of decaying organic matter enriches the soil and provides a fertile environment for plants to thrive.

2. Nomadic tribespeople are becoming more sedentary, leading to over cultivation. How is over cultivation defined?

Not planting enough crops to allow the soil to be protected from the rain

Planting more crops than can be watered, leading to death of some of the crops

The excessive use of farmland to the point where productivity falls due to soil exhaustion or land degradation

Adding too much fertiliser, leading to eutrophication of the streams and waterways.

Over cultivation is defined as the excessive use of farmland to the point where productivity decreases due to soil exhaustion or land degradation. This occurs when the land is continuously used for cultivation without allowing it enough time to recover and replenish its nutrients. As a result, the soil becomes depleted, leading to a decline in crop yields. This can also result in land degradation, where the quality and fertility of the soil deteriorate, making it less suitable for agriculture in the long run.

Explanation

Over cultivation is defined as the excessive use of farmland to the point where productivity decreases due to soil exhaustion or land degradation. This occurs when the land is continuously used for cultivation without allowing it enough time to recover and replenish its nutrients. As a result, the soil becomes depleted, leading to a decline in crop yields. This can also result in land degradation, where the quality and fertility of the soil deteriorate, making it less suitable for agriculture in the long run.

3. What form of erosion occurs when intense rainfall cuts small streams into slopes in areas with little or no vegetation cover?

Sheet Erosion

Gully Erosion

Wind Erosion

Salinisation

Gully erosion occurs when intense rainfall cuts small streams into slopes in areas with little or no vegetation cover. The force of the rainfall causes the water to flow rapidly, carrying away soil and creating deep channels or gullies. This type of erosion is common in areas with steep slopes and heavy rainfall, where the water is not able to be absorbed by the soil or vegetation. Gully erosion can lead to significant soil loss and land degradation, making it an important issue in land management and conservation.

Explanation

Gully erosion occurs when intense rainfall cuts small streams into slopes in areas with little or no vegetation cover. The force of the rainfall causes the water to flow rapidly, carrying away soil and creating deep channels or gullies. This type of erosion is common in areas with steep slopes and heavy rainfall, where the water is not able to be absorbed by the soil or vegetation. Gully erosion can lead to significant soil loss and land degradation, making it an important issue in land management and conservation.

4. What is the danger of soil being left bare in hot, dry zones?

Desertification as the soil blows away, leaving only the heavier sand grains

Weeds will grow rampant, preventing crops from growing

Build up of dry soils as the bare patch spreads

The nutrients will be leached away by the Sun

When soil is left bare in hot, dry zones, the lack of vegetation and organic matter makes it more susceptible to erosion by wind. As a result, the top layer of soil can be blown away, leaving behind only the heavier sand grains. This process is known as desertification and can lead to the degradation of land, loss of fertile soil, and the transformation of once habitable areas into desert-like conditions.

Explanation

When soil is left bare in hot, dry zones, the lack of vegetation and organic matter makes it more susceptible to erosion by wind. As a result, the top layer of soil can be blown away, leaving behind only the heavier sand grains. This process is known as desertification and can lead to the degradation of land, loss of fertile soil, and the transformation of once habitable areas into desert-like conditions.

5. On many islands and in some nature reserves, goats are being removed and banned. How does removing goats and similar grazing animals reduce soil erosion?

Goats tend to move around a lot, stirring up soil and leaving it open to erosion

Goats will often overgraze areas and remove all vegetation, leaving bare earth

The excess organic matter from the goats' droppings leads to pockets of rapid plant growth

Goats discourage other animals that may help the plants to grow

When goats overgraze an area, they consume all the vegetation, leaving the soil exposed and vulnerable to erosion. Vegetation plays a crucial role in preventing soil erosion as the roots of plants hold the soil in place, preventing it from being washed away by rain or wind. Without vegetation, the soil becomes loose and easily eroded. Therefore, removing goats and similar grazing animals helps reduce soil erosion by preventing overgrazing and preserving the vegetation cover that protects the soil.

Explanation

When goats overgraze an area, they consume all the vegetation, leaving the soil exposed and vulnerable to erosion. Vegetation plays a crucial role in preventing soil erosion as the roots of plants hold the soil in place, preventing it from being washed away by rain or wind. Without vegetation, the soil becomes loose and easily eroded. Therefore, removing goats and similar grazing animals helps reduce soil erosion by preventing overgrazing and preserving the vegetation cover that protects the soil.

6. Which of the following is not a method of soil conservation?

Planting hedges

Terraces

Contour ploughing

Slash and burn agriculture

Slash and burn agriculture is not a method of soil conservation because it involves cutting down and burning vegetation in an area before planting crops. This practice depletes the nutrients in the soil and leads to soil erosion, making it unsustainable for long-term agricultural use. On the other hand, planting hedges, terraces, and contour ploughing are all methods that help to prevent soil erosion, improve soil fertility, and conserve soil for sustainable agriculture.

Explanation

Slash and burn agriculture is not a method of soil conservation because it involves cutting down and burning vegetation in an area before planting crops. This practice depletes the nutrients in the soil and leads to soil erosion, making it unsustainable for long-term agricultural use. On the other hand, planting hedges, terraces, and contour ploughing are all methods that help to prevent soil erosion, improve soil fertility, and conserve soil for sustainable agriculture.

7. Heavy machinery often leads to soil compaction. How does soil compaction lead to soil erosion?

The solid soil is removed in blocks rather than in small amounts

The solid soil prevents water from percolating into the soil and increases surface runoff

The compacted soils will be lower and encourage water to pool and soil to be washed away

The machines remove large amounts of soil on their tyre treads

Soil compaction leads to soil erosion because when the soil is compacted, it becomes denser and less permeable, preventing water from infiltrating into the soil. This results in increased surface runoff, as the water is unable to penetrate the compacted soil and instead flows over the surface. The increased surface runoff carries away the top layer of soil, causing erosion.

Explanation

Soil compaction leads to soil erosion because when the soil is compacted, it becomes denser and less permeable, preventing water from infiltrating into the soil. This results in increased surface runoff, as the water is unable to penetrate the compacted soil and instead flows over the surface. The increased surface runoff carries away the top layer of soil, causing erosion.

8. What happens to the soil when salinisation occurs?

During storms, sea water washes in and contaminates plants

Salts and other minerals are washed out of the soil during heavy rains

Water evaporates in high temperatures drawing salts from the soil to the surface

Flood water removes all the other soil particles except salt

Salinisation occurs when the water in the soil evaporates in high temperatures. As the water evaporates, it draws the salts from the soil to the surface, leading to an increase in salt concentration. This process can be detrimental to plant growth as high levels of salt can hinder the absorption of water and nutrients by the plants.

Explanation

Salinisation occurs when the water in the soil evaporates in high temperatures. As the water evaporates, it draws the salts from the soil to the surface, leading to an increase in salt concentration. This process can be detrimental to plant growth as high levels of salt can hinder the absorption of water and nutrients by the plants.

9. What type of erosion occurs when moderate rainfall on bare soil removes the topsoil down-slope?

Sheet Erosion

Gully Erosion

Wind Erosion

Salinisation

Sheet erosion occurs when moderate rainfall on bare soil removes the topsoil down-slope. This type of erosion is characterized by a thin layer of soil being washed away uniformly, creating a sheet-like pattern. It is commonly observed in areas with minimal vegetation or ground cover, where rainwater can easily flow over the surface and carry away the loose soil particles. Sheet erosion can lead to the loss of fertile topsoil, decreased soil quality, and reduced agricultural productivity.

Explanation

Sheet erosion occurs when moderate rainfall on bare soil removes the topsoil down-slope. This type of erosion is characterized by a thin layer of soil being washed away uniformly, creating a sheet-like pattern. It is commonly observed in areas with minimal vegetation or ground cover, where rainwater can easily flow over the surface and carry away the loose soil particles. Sheet erosion can lead to the loss of fertile topsoil, decreased soil quality, and reduced agricultural productivity.

10. When a field is ploughed, why is it best to plough at right angles to the slope?

Ploughing parallel can lead to machines toppling over

Ploughing at right angles to the slope improves plants' chances at getting equal sunlight

Ploughing parallel to the slope draws the soil downhill

Ploughing parallel to the slope can increase gully erosion

Ploughing parallel to the slope can increase gully erosion because it allows water to flow directly downhill, causing the soil to erode and form gullies. Ploughing at right angles to the slope helps to prevent this erosion by creating ridges or furrows that slow down the flow of water and reduce the risk of gully formation.

Explanation

Ploughing parallel to the slope can increase gully erosion because it allows water to flow directly downhill, causing the soil to erode and form gullies. Ploughing at right angles to the slope helps to prevent this erosion by creating ridges or furrows that slow down the flow of water and reduce the risk of gully formation.