Our 18 day venture, organised by Bristol University Geology Department, took us on a scenic tour across the states of Nevada, Utah, Arizona and California, where we visited a wealth of National Parks with geological formations so numerous and on such a grand scale that we have hardly stopped enthusing over or talking about the trip ever since.
The flora and fauna of this area is as rich and varied as the geology, from the many varieties of cacti and desert flowers including the brightly coloured Indian Paintbrush, to chipmunks and tiny lizards which scamper about everywhere. And archaeology too, for long before white man became established in the New World, Red Indians scraped a living from the parched desertlands of Utah and Arizona, and their ancient homes can be seen today along the valley floors or perched precipitously on ledges of rock in sheer canyon walls. One group of Indians, the Sinagua, meaning literally “without water”, learnt to farm the fertile basalt-rich soils of the San Francisco Volcanic Field in central Arizona. They discovered that a covering of cinders and ash prevented the evaporation of moisture from the soil, and they built their homes dangerously close to the volcanic peaks. When Sunset Crater erupted in 1064 AD, many of their homes were destroyed, but far from driving them out, the fresh supply of ash and cinders attracted many more Indians.
During our tour there were so many highlights with each day offering new and exciting scenery - and such diversity, for every National Park was so different and each really had a character all its own. There was Bryce Canyon with its intricate maze of rock pinnacles, the Petrified Forest with its fabulous collection of fossilised wood, Canyon de Chelly with its red walls harbouring ancient Indian dwellings, and the geologic wonder of the world, the majestic Grand Canyon. Choosing one locality from so many is an almost impossible task, but Arches National Park is of particular interest and worthy of a mention, for it contains a marvellous variety of natural rock formations, from huge sandstone monliths resembling Egyptian temples, to balanced rocks which seem to defy gravity and naturally formed arches which give the park its name.
The Park, a high desert area between 4000 and 5600 feet above sea level, is located in southeast Utah, in the so called red-rock country, named after the vivid colours of the sandstone which forms such a spectacular part of the scenery in the South West. The Park runs across part of the Salt Valley Anticline and was thus subject to doming and upfolding which produced a series of parallel joints in the two rock Formations present here. One Formation, the desert-lain Jurassic Entrada Sandstone, is particularly susceptible to jointing, and in time weathering enlarged these joints to produce a series of upstanding rock “fins”, The Entrada Sandstone varies in hardness due to uneven cementing of its sand grains, and further erosion by the action of running water, wind and frost through weak portions in these rock fins has produced the amazing natural arches. In the Park can be seen many arches in their various stages of formation, from the massive rock fins - arches in the making, to slender, graceful arches worn so thin that they are now near the point of collapse. During our time in the Park, we viewed many such formations, and two particularly spectacular arches which involved walks along dusty trails with temperatures well into the 80s. The first arch, named Landscape, was a magnificent structure which, with a span of almost 300 feet, is the longest known natural arch in the world. The second arch, named Delicate, involved a round trip of 3 miles, on a trail which rose over 500 feet across the Navajo Sandstone, a quite exhausting climb in the heat of mid afternoon, But all of us who attempted the climb would not have missed it for the world. The end of the trail took us along a narrow ledge which shielded the arch from view until the very last moment. Then Delicate Arch revealed itself to us in all its glory, rising 85 feet above the slickrock surface. And what a magnificent setting it was, surrounded by the distant peaks of the La Sal Mountains, their summits sprinkled white after the first snow fall of the Autumn.
Arches National Park was just one of about 20 different National Parks, National Monuments and canyons we visited during our tour which took us over 2500 miles across the South West. Some of us even found time to see a show in Las Vegas, or meet Mickey Mouse in Disneyland! All 40 of us who went, even that dedicated trio of geologyists from Bristol University who led our party so efficiently and did not succeed in losing a single one of us in America, had a thoroughly enjoyable time.