Roadside Geology of Arizona
Halka Chronic
Language: English
Pages: 322
ISBN: 0878421475
Format: PDF / Kindle (mobi) / ePub
Roadside Geology of Hawai`i details the evolution of this volcanic island chain, from the origin of a hot spot and the tumultuous creation of each island to ongoing eruptions and the gradual death and erosion of old volcanoes. Residents and tourists alike will soon become experts on lava tubes and lava flows, ancient beaches and coral reefs, ephemeral black sand beaches and the occasional tsunami. Includes a chapter each on six easily accessible and populated islands: Hawai`i , Maui, Lana`i, Moloka`i, O`ahu, and Kaua`i. Each chapter begins with a general discussion of the rocks of that island, then proceeds with a seres of road guides that provide the local details.
Arizona's pull-apart and push-together story can only be related in respect to time. Geologic time begins, of course, with the birth of geos, the earth, about 4.5 billion years ago. That's 4,500,000,000 years- a long, long, long time by any measure. Geologists divide that immensity of time into eras, periods, and epochs, somewhat as calendars divide a human lifetime into years, months, and days. But the geologic units are not as 7 uniform as calendar units. The first era, the Precambrian
fatalities. The 1980 storm closed eight of the area's ten bridges of the Salt River. Water from several dams farther up the river and from deep wells irrigates citrus orchards, cotton and bean fields, and other croplands in the Phoenix area. Pumping of groundwater in the Salt River Valley has led to land subsidence and fissuring. It's quite apparent that in the deserts of Arizona, water tells people where to live and where to farm. The abundant waters of the Salt River dictated the location and
them. Near milepost 46 this valley lies on steeply tilted, reddish, bouldery conglomerate that may have been a land slide or mudflow deposit. To the west, out of sight, is the Helvetia-Rosemont Mining District, with a porphyry copper deposit estimated to contain 340million tons of copper ore. This district also contains placer gold and is a weekend favorite with amateur gold panners. Like the Whetstones, the Empire Mountains display Paleozoic and Cretaceous sedimentary rocks, but they are not as
Tertiary lake sediments: flat-lying layers of whitish limestone, siltstone, and water-laid volcanic ash; • Precambrian granite: grainy tan or light gray rock that weathers to rounded boulders and knobs; • Precambrian metamorphic rock, mostly flaky, silvery schist. • As you can see, Cenozoic rocks lie right on or against Precambrian ones here. The absence ofPaleozoic and Mesozoic rocks was for a long time taken to mean that the Central Highlands had been a topo graphic high all though Paleozoic
characteristics of each. The mountains to the north, a melange of Tertiary and Quaternary volcanic rocks, are classed as part of the Central Highlands. In fragments along their southern edge - in deep canyons like that of the San Francisco River - we find large masses of Precambrian igneous and metamorphic rock and smaller patches of much faulted Paleozoic rock similar to those that make up other parts of the Central Highlands. These little patches are especially tantalizing because where they