Breaking Down the Earth: Weathering Types Quiz

If physical weathering occurs, then the rock is broken into smaller pieces of the same material. If chemical weathering occurs, then the internal molecular structure is altered. If the identity of the substance changes, then it is chemical weathering.

If water enters a crack in a rock, then it occupies a specific volume. If that water freezes, then it expands by about 9%. If the expansion creates outward pressure, then the rock splits, which is the physical process of ice wedging.

If iron-bearing minerals in a rock are exposed to oxygen and water, then a chemical reaction occurs. If this reaction produces iron oxide (rust), then the rock's composition has been changed through oxidation.

If rocks are carried by moving water, then they collide with one another. If these collisions wear down the sharp edges and break off small fragments, then the physical process of abrasion is occurring.

If CO2 in the atmosphere mixes with falling rain, then a chemical reaction occurs. If this reaction creates a weak acid capable of dissolving minerals like limestone, then that acid is carbonic acid.

If a rock is broken into many pieces, then more of its interior is exposed to the outside. If more area is exposed to air and water, then there are more places for chemical reactions to occur, increasing the rate.

If an organism like a lichen grows on a rock, then it releases organic acids as a metabolic byproduct. If these acids slowly dissolve the minerals beneath the organism, then it is performing chemical weathering.

If wind blows sand against a cliff, if water tumbles rocks in a stream, or if rocks fall down a slope, then they strike other surfaces. If these impacts physically wear away the rock, then all three are agents of abrasion.

If limestone is primarily made of the mineral calcite, then it is highly reactive to acids. If carbonic acid comes into contact with calcite, then it dissolves the mineral quickly compared to other rock types.

If salt water enters rock cracks and evaporates, then salt crystals are left behind. If those crystals grow larger, then they exert physical pressure on the rock walls. If that pressure is high enough, then the rock breaks.

If particles act like sandpaper against a larger rock surface, then they wear that surface down. If this is a mechanical process of friction and impact, then the term is abrasion.

If a plant root grows into a crevice, then it exerts physical pressure as it expands. If the pressure causes the rock to break without changing its mineral makeup, then it is a physical process, not a chemical one.

If a large mass of rock is buried, then it is under great pressure. If the overlying material is eroded away, then the rock expands. If the outer layers crack and fall off like an onion, then it is called exfoliation.

If a process breaks rock without changing its chemical identity, then it is physical. If ice expands, animals dig, or rocks expand/contract from heat, then the rock breaks physically.

If a substance reacts with minerals to create new compounds, then it is a chemical agent. If oxygen causes rust, water dissolves minerals, or acids break down bonds, then they are chemical agents.

If water molecules react directly with mineral crystals to change their structure, then a chemical change occurs. If this specific reaction creates clay minerals, then the process is defined as hydrolysis.

If oxygen reacts with iron in the presence of moisture, then it forms iron oxide. If this results in a reddish-brown coating on the rock, then the chemical process is called oxidation.

If stalactites form from minerals dissolving in water and then redepositing, then the process involves chemical changes and solutions. If it involves changing the state and composition of the minerals, then it is chemical, not physical.

If temperatures fluctuate around freezing, then ice wedging occurs more often. If slopes are steep, then gravity causes more impacts. If plants grow in cracks, then they force rocks apart.

If chemical reactions generally speed up with increased temperature, then heat promotes weathering. If water is a primary agent for most chemical changes, then high humidity increases the rate. If both are present, then weathering is fastest.