Chemical weathering of rocks is much greater in a place with

The correct answer is B, hot and humid climate. Chemical weathering is the breakdown of rocks through reactions such as solution, oxidation, carbonation and hydration, and all of these need water. Heat speeds up chemical reactions, so the combination of high temperature and plenty of moisture, found in equatorial and tropical rainforest regions, makes chemical weathering most intense. This is why the tropics have deep weathered layers and soils such as laterite, which forms by heavy leaching under high heat and rainfall. Option A is wrong because in a cold and dry climate there is little water and reactions are slow, so chemical weathering is weakest. Option C is wrong because hot deserts lack moisture; there, mechanical weathering dominates, as rocks crack under the large daily range of temperature. Option D is wrong because, although water is available, low temperatures slow the reactions; in cold regions frost wedging, a mechanical process, is more important. Exam tip: hot and wet = chemical weathering; hot and dry = mechanical weathering by temperature change; cold and wet = frost action.