Shaping the relief

Define and order the four stages of the cycle of action of an external agent: erosion, weathering, deposition, and transport.

Distinguish between erosion, transport and sedimentation using the journey of a rock particle from a mountain slope to the bottom of a lake, indicating which agent intervenes at each stage.

Differentiate between physical and chemical weathering, describing two processes of each type (for example freeze-thaw weathering, thermal shattering, dissolution, or oxidation) and the climate in which each is most effective.

State four external agents of landform shaping and name a characteristic landform for each, indicating whether it is erosional or depositional.

Explain what freeze-thaw shattering is, what climatic conditions it needs (alternating frosts and thaws) and in which areas of Spain it is most intense today (high mountains: Picos de Europa, Sierra Nevada, the Pyrenees).

The granite boulder fields of La Pedriza show stacked, rounded blocks. Explain the spheroidal weathering of granite (alteration guided by the joints, peeling off in layers) and why it produces those "ball" and tor shapes.

What is a meander? Explain how it grows and shifts laterally (erosion on the concave bank and deposition on the convex one) and what form remains when the river cuts it off and abandons it.

Explain step by step how a delta forms at the mouth of a river and indicate what condition must be met for the delta to advance rather than be eroded by the sea.

What is the base level of a river? Explain what happens to the channel when sea level falls (incision) or rises (filling of the mouth) and apply it to the history of the Ebro delta during sea-level changes.

What is karst topography, on what type of rock does it develop, and what chemical process explains it? Give an example of a surface karst feature and a subterranean one.

In a karst massif, calcium carbonate dissolution rates four times higher are recorded under a deciduous forest with a thick humic horizon than in an adjacent area of completely bare limestone exposed to the same annual precipitation.

1. a) Justify this difference based on the chemical equilibrium $\text{CaCO}_3 + \text{CO}_2 + \text{H}_2\text{O} \rightleftharpoons \text{Ca}^{2+} + 2\,\text{HCO}_3^-$, explaining the origin of soil $\text{CO}_2$ and predicting how the equilibrium shifts when water percolates into a ventilated underground cavern.
2. b) The route of a motorway detects a straight alignment of sinkholes (dolines) on the surface. Interpret what underlying geological discontinuity this arrangement reveals and predict what immediate geological hazard massive groundwater pumping from the karst aquifer to dewater the foundations would pose.
3. c) A soluble toxic chemical is accidentally spilled at the bottom of a karst pothole (chasm). Justify why the retention, attenuation, and filtration models typical of detrital aquifers (sands or gravels) are not valid for predicting the dispersion of this contaminant within the karst system.

Distinguish between a cliff coast and a beach coast: which lithology and which marine dynamics favour each one, and name a Spanish stretch of each type.

Explain how the wind shapes the landscape: what deflation is, how sand is transported (saltation) and how a barchan dune forms and advances, indicating what role vegetation plays in fixing it.

Describe the formation of a glacial cirque and of a U-shaped glacial valley, and name two valleys in Spanish mountains where these forms can be seen today even though the ice no longer exists (the Pineta valley, the Ordesa valley).