Although mineral hazards are generally not well established in the public consciousness compared to other natural hazards, they can adversely affect public health and safety and the environment. The term “mineral hazards,” as used here, includes certain naturally occurring earth materials and sites of man-made activities related to them, such as mining and oil drilling. Since the 1990s, the California Geological Survey has conducted many studies of mineral hazards in California in response to an increasing number of requests from government agencies, private industry, and the public. These studies have focused mostly on naturally occurring asbestos, radon, and various metals, such as mercury and cadmium. The mineral-hazard maps and companion reports produced from these studies are typically at statewide and regional scales. They are designed for use by nongeoscientists and geoscientists alike in an effort to educate these groups about mineral hazards and to help in mitigation of those hazards. These products indicate the likelihood of the occurrence of a mineral hazard at a given location, but not the associated health risk. Geographic information systems (GIS) are used to manage and analyze data, and to design the maps. The variety of products developed ranges from traditional paper maps to thematic digital layers for use in a GIS. This range of products increases the likelihood that a greater number of people will use the information. The maps and reports have been used in many applications, and additional applications await development as awareness of mineral hazards and the need for mitigation of them increase.

Based on relationships among volcanic-plutonic arc rocks, high-pressure–low-temperature (HP-LT) metamafic rocks, westward relative migration of the Klamath Mountains salient, and locations of the Mariposa-Galice, Great Valley Group, and Franciscan depositional basins, the following geologic evolution is inferred for the northern California continental edge: (1) By ca. 175 Ma, onset of transpressive plate underflow generated an Andean-type Klamath-Sierran arc along the margin. At ca. 165 Ma and continuing to ca. 150–140 Ma, erosion supplied volcanogenic debris to proximal Mariposa-Galice ± Myrtle overlap strata. (2) Oceanic crustal rocks were metamorphosed under HP-LT conditions in an inboard, east-inclined subduction zone from ca. 165 to 150 Ma. Most such mafic rocks remained stored at depth, and HP-LT tectonic blocks only returned surfaceward during the Late Cretaceous, chiefly entrained in circulating, buoyant Franciscan mud-matrix mélange. (3) At end-of-Jurassic time, before onset of paired Franciscan and Great Valley Group + Hornbrook deposition, the Klamath salient was deformed and displaced ∼100–200 km westward relative to the Sierran arc. (4) After this ca. 140 Ma seaward step-out of the Farallon–North American convergent plate junction—stranding preexisting oceanic crust on the south as the Coast Range ophiolite—terrigenous debris began to arrive at the Franciscan trench and intervening Great Valley forearc. Voluminous sedimentation and accretion of Franciscan Eastern + Central belt and Great Valley Group coeval detritus took place during paroxysmal igneous activity and rapid, nearly orthogonal plate convergence at ca. 125–80 Ma. (5) Sierran arc volcanism-plutonism ceased by ca. 80 Ma in northern California, signaling a transition to shallow, nearly subhorizontal eastward plate underflow attending Laramide orogeny far to the east. (6) Paleogene–Lower Miocene Franciscan Coastal belt sedimentary strata were deposited in a tectonic realm nearly unaffected by HP-LT subduction. (7) Grenville-age detrital zircons apparently are absent from the post–120 Ma Franciscan section. Detritus from the Pacific Northwest is not present in the Central belt sandstones, whereas zircons from the Idaho Batholith, the Challis volcanics, and the Cascade Range appear in progressively younger Paleogene–Lower Miocene Coastal belt sediments. This trend suggests the possible gradual NW dextral offset of Franciscan trench deposits of up to ∼1600 km relative to the autochthonous Great Valley Group forearc and basement terranes of the American Southwest.

Abstract In this volume we present seven field trip guides that span the breadth of the geology of central California. The trips are associated with the 2013 Cordilleran Section meeting of the Geological Society of America, convened in Fresno, California. These trips provide guides to some of the most remarkable of geologic localities, which are not only iconic, but form type examples of key geologic phenomena and include Yosemite National Park, the San Andreas fault, the Franciscan complex, and the Sierra Nevada Foothills near Fresno, California. The topics covered by these field trips include the nature of continental transform faults, the initiation of subduction, the origin of the Sierra Nevada batholith, the initiation of the Sierra Nevada arc, Pleistocene vertebrate fossils of the Central Valley, and debris flows triggered from burned watersheds.

Mima mounds, often associated with vernal pools, have historically been shrouded in genetic uncertainty. Nevertheless, emerging from the array of explanations proposed, a biological mechanism for mound formation has steadily gained strength. We use innovations in remote sensing and geomorphic modeling to develop a new approach to evaluate the microtopography. Using a digital elevation model created from LIDAR (light detection and ranging) data, morphometric values—average mound diameters, heights, slopes, and curvatures—were calculated across an 18 km 2 sector of a mound-pool region that covers an ancient river terrace near Merced, California. The terrain information was applied to a sediment transport model to estimate mound erosion and swale deposition rates. The mean net erosion rate was 38 cm kyr −1 , using a diffusion coefficient of 50 cm 2 yr −1 . At steady state, erosion must be balanced by a restorative upslope transport, and this estimate of erosion is comparable to observed rates of sediment mounding via pocket gopher burrowing (61 cm kyr −1 ). These data suggest that bioturbation may play a dominant role in maintaining Mima mound terrain. LIDAR measurements were also used to develop a model that approximates the energy required for the formation of Mima mounds (shearing, pushing, and uplifting soil) and their maintenance (counteractions to erosion). This energy estimate was compared to estimates of energy available to gopher populations in the region. Our results indicate that gophers have ample energy to build typical Mima mounds in as little as 100 years, thus strongly supporting a biotic mechanism of Mima mound development and maintenance.