Studies of long-term landscape development have traditionally relied to a significant extent on the interpretation of morphological features, such as erosion surfaces and river long profiles, and their correlation with deposits of known or inferred age. The success of this approach has been limited by the paucity of datable deposits due to the preponderance of net erosion in most landscapes. Thermochronology and cosmogenic isotope analysis, however, are two sets of techniques capable of providing valuable estimates of long-term denudation rates in eroding landscapes by quantifying the time elapsed as a rock sample moves from a known depth to the surface. For the majority of geomorphological applications the most useful thermochronometer is apatite fission-track analysis. This can yield cooling histories across a temperature window from ~125 to 60°C which can be used to infer denudational histories for crustal depths of up to ~4 km for common geothermal gradients. Recently, partial retention of He between ~75 and ~40°C has been demonstrated in the U-Th/He system and this could potentially be used to estimate denudation at shallower depths of ~2 km.

The regional-scale variations in long-term (10⁶-10⁸ a) denudation rates inferred from these thermochronological techniques can be combined with more site-specific data from cosmogenic isotope analysis which yield estimates of denudation rates over shorter timescales of 10³-10⁶ a. The integration of these complementary techniques, and their role in constraining landscape evolution models, is illustrated with reference to the development of the landscape of southern African using data from ¹⁰Be, ²⁶Al and ³⁶Cl cosmogenic isotope analysis and apatite fission-track analysis.