Abstract

Landscape change occurs on a wide range of spatial and temporal scales. Changes within volcanic terrains are often some of the most dynamic due to the types of processes that form these landscapes and the inherent properties of volcanic deposits. As a consequence volcanic terrains often form unique, weird and wonderful geomorphological features and landscapes, understanding which can teach us much about both the volcanic deposits and the forces that shaped them. This dissertation explores examples of volcanic geomorphology using field- and space-based remote sensing data, along with field-based observations.

Studies were made of the landscapes at La Pacana Caldera (Chile), Valles Caldera (New Mexico, USA) and Mt. Etna (Italy). For La Pacana Caldera, LANDSAT and SRTM images were used to identify erosional ridges and channels (across 100s km²), within several surrounding ignimbrite sheets that were predominantly erupted during a period of major activity ∼4 and 5 Ma ago. Most notable was a coherent NW-SE alignment of many of the erosional features, possibly offering clues about the past stability of the regional climate.

At Valles Caldera the geomorphology of interest occurred on a smaller scale, at more isolated locations. Eroded columns of ignimbrite, <1 m in diameter, but up to 20 m high, are exposed in several valley walls. These volumes of ignimbrite were found to have undergone alteration making them more resistant to erosion than the rest of the host deposit. A model for the mechanism by which they formed is postulated and draws significant inspiration form observations made of the erosion of the 1991 Mt. Pinatubo Ignimbrite sheet.

The environment at Mt. Etna is different than in the other two studies as it is predominantly basaltic lava. Also, the dynamic changes studied occurred during emplacement, rather than the subsequent erosion. Observations concentrated on an open lava channel, which demonstrated cyclical behavior in its flow patterns. This in turn influenced the style of lava emplacement around the channel and the morphology of landscape features. Overall this dissertation provides a diverse look at geomorphological changes in volcanic landscapes that highlight the dynamic processes shaping the landscape of our Earth and other planetary bodies.