Abstract Fans, landforms that record the storage and transport of sediment from uplands to depositional basins, are found on Saturn’s moon Titan, a body of significantly different process rates and material compositions from Earth. Images obtained by the Cassini spacecraft’s synthetic aperture radar reveal morphologies, roughness, textural patterns and other properties consistent with fan analogues on Earth also viewed by synthetic aperture radar. The observed fan characteristics on Titan reveal some regions of high relative relief and others with gentle slopes over hundreds of kilometres, exposing topographic variations and influences on fan formation. There is evidence for a range of particle sizes across proximal to distal fan regions, from c. 2 cm or more to fine-grained, which can provide details on sedimentary processes. Some features are best described as alluvial fans, which implies their proximity to high-relief source areas, while others are more likely to be fluvial fans, drawing from larger catchment areas and frequently characterized by more prolonged runoff events. The presence of fans corroborates the vast liquid storage capacity of the atmosphere and the resultant episodic behaviour. Fans join the growing list of landforms on Titan derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between these two planetary bodies.

Southern California, extending from Point Conception (34 1/2 °N) to the Tijuana estuary (32° N), has a varied and attractive coastline, with a moderate Mediterranean climate and a large human population. Rapid urban development has resulted in coastal modification for shipping, military, industrial, housing and recreational needs. Because of their flat topography and availability of water, the coastal wetlands have been the prime target for these modifications. According to Zedler (1982, p.l), the ‘disturbance has been so pervasive, taken such different forms, and had such different results in each wetland, that sorting out natural and unnatural features is extremely difficult’. Southern California coastal wetlands are small and discrete, confined to narrow river valleys, and separated by coastal hills, mountains, harbors and extensive urban tracts. There are about 30 wetlands, occupying a total area of about 12,500 acres (Fig 1) which represent about 10% of their extent prior to arrival of Europeans. The wetlands occur on intertidal slopes and along the mouth of creeks, and support a variety of salt tolerant plants, called halophytes. Poised at the edge of both land and sea, these habitats receive fresh water, sediments and nutrients from the watershed, and tidal water with its salts, minerals and sands from the sea. At some locations, coastal dunes enclose these wetlands and occasionally, sand bars form, cutting off tidal circulation. This has resulted in decimation of certain plant communities and dependant bird populations.

Yucca Mountain has been proposed as the site for the nation's first geologic repository for high-level radioactive waste. This chapter provides the geologic framework for the Yucca Mountain region. The regional geologic units range in age from late Precambrian through Holocene, and these are described briefly. Yucca Mountain is composed dominantly of pyroclastic units that range in age from 11.4 to 15.2 Ma. The proposed repository would be constructed within the Topopah Spring Tuff, which is the lower of two major zoned and welded ash-flow tuffs within the Paintbrush Group. The two welded tuffs are separated by the partly to nonwelded Pah Canyon Tuff and Yucca Mountain Tuff, which together figure prominently in the hydrology of the unsaturated zone. The Quaternary deposits are primarily alluvial sediments with minor basaltic cinder cones and flows. Both have been studied extensively because of their importance in predicting the long-term performance of the proposed repository. Basaltic volcanism began ca. 10 Ma and continued as recently as ca. 80 ka with the eruption of cones and flows at Lathrop Wells, ∼10 km south-southwest of Yucca Mountain. Geologic structure in the Yucca Mountain region is complex. During the latest Paleozoic and Mesozoic, strong compressional forces caused tight folding and thrust faulting. The present regional setting is one of extension, and normal faulting has been active from the Miocene through to the present. There are three major local tectonic domains: (1) Basin and Range, (2) Walker Lane, and (3) Inyo-Mono. Each domain has an effect on the stability of Yucca Mountain.