100+ Free BGCSE Geography Practice Questions

Explanation: Exfoliation occurs when outer rock layers expand during hot days and contract during cold nights, causing peeling of rock layers. In semi-arid regions like the Kalahari with high diurnal temperature ranges and sparse vegetation, this physical weathering process is particularly dominant.

Explanation: Carbonation occurs when atmospheric carbon dioxide dissolves in rainwater to form weak carbonic acid. When this acidic rainwater contacts rocks containing calcium carbonate (such as limestone or dolomite), it converts insoluble calcium carbonate into soluble calcium bicarbonate, leading to solution features like caves and sinkholes.

Explanation: Freeze-thaw weathering requires temperature fluctuations across the freezing point (0°C) along with water entering rock crevices. As water freezes into ice, it expands by approximately 9%, exerting immense outward pressure on the rock walls, eventually causing fragments to break off as scree.

Explanation: Biological weathering involves plants and animals breaking down rock. Tree and plant roots wedge into existing joints and cracks in rocks; as the roots grow thicker, they exert mechanical pressure that splits the rock apart. Lichens also produce organic acids that chemically weather rock surfaces.

Explanation: Hydraulic action is the mechanical erosion caused by the force of moving water. As water surges into cracks in the river bed and banks, air is trapped and compressed. When the water recedes, the sudden release of pressure causes explosive cavitation that weakens and dislodges rock fragments.

Explanation: An oxbow lake forms on a river floodplain when lateral erosion on the outer bends of a meander narrows the meander neck. During a flood, the river takes the straightest path and cuts directly through the neck. Subsequent deposition seals off the ends of the abandoned meander loop, leaving a crescent-shaped oxbow lake.

Explanation: Waterfalls form where a layer of resistant hard rock overlies weaker soft rock. As water falls over the ledge, hydraulic action and abrasion erode the softer rock beneath at a faster rate, creating a plunge pool and undercutting the hard rock overhang. Eventually, the unsupported overhang collapses under gravity, causing the waterfall to retreat upstream and leave a steep gorge.

Explanation: The Okavango Delta is an inland delta because the Okavango River flows from the Angolan highlands into a tectonic trough in the semi-arid Kalahari Desert. Instead of draining into an ocean, the water spreads across a vast alluvial fan (15,000–22,000 sq km) where over 95% of the water evaporates or transpires.

Explanation: Due to centrifugal force, the fastest-flowing current (thalweg) swings to the outer bend of a meander. High velocity and friction cause intense lateral erosion (hydraulic action and abrasion) on the outer bank, undercutting it to form a steep river cliff. Conversely, slow velocity on the inner bank promotes deposition, forming a slip-off slope.

Explanation: At a divergent (constructive) boundary, tectonic plates pull apart due to tensional forces driven by mantle convection currents. As the plates separate, magma rises from the asthenosphere to fill the gap, cooling to form new oceanic or continental crust (e.g., Mid-Atlantic Ridge, East African Rift).