Great landforms created by geologic processes:

Crater Lake (above), located in southern Oregon, is what remains of an extinct volcano. Volcanoes are often the result of tectonic plates colliding. The North American continental plate collided with the Pacific plate millions of years ago, forming volcanoes along the west coast that once rivaled the Andes. The Cascade Range, of which Crater Lake is a part, represent a more recent round of activity. As the oceanic plate dives into a miles-deep trench near the coastline and moves under the continental plate, the salt water is boiled off and the ocean floor (crust) is melted in the earth's mantle. The resulting magma surges up through the continental crust to form volcanoes along the coast.

Florida, Africa, Alaska and Antarctica:

The zones where plates have collided (millions or billions of years ago) are often defined by interesting structures. For example, the state of Florida was once part of Africa. Along that same theme, Alaska was smeared along the west coast, eventually halting its slide in the northwest. The plate that brought it, perhaps a very young Antarctica or Australia, left its signature as the state of Alaska and much of the land to the south, all the way to the California coast. When a plate drifts in and collides with the coastline, it often scrapes up deep segments of ocean floor and shoves them against the target continent, North America in this case. You can hike in mountains in California, Arizona and New Mexico, or drive Interstate 80 through the Rocky Mountains, and you'll find, warped into the rock, sometimes along road cuts, pieces of formerly deep ocean crust (known to geologists as Ophiolites) hundreds of miles from the coast.

Hotspots:

The Appalachian Mountains, on the east coast, tell another story. The continents that are now Europe, South America and Africa, drove so hard into the east coast their impact lifted the Appalachians, more than once. The Great Smoky Mountains, one of the most beautiful hiking terrains on the east coast, is an example of that mountain building event (geologists call it an Orogeny). But there is a strange twist, one you might sense on the trail. The evidence of these collisions does not explain a recent move upward by the Smokies. Sure, millions of years ago, you could stand on the Great Smoky summit and see Africa come on board, drive you higher and then, millions of years later, sail off toward its current location. But what caused the recent elevation? There is some consensus that a huge molten bubble of magma deep underground may have been the agent. The bubble (hotspot) has now moved offshore and is thought to be under Bermuda. Although in reality, it's not the hotspot that moved. The continental and oceanic plates that carry North America and the Atlantic Ocean have moved in a westerly direction over the hotspot, which is stationary and located deep under the crust in the earth's mantle. And what about a strange variety of granite-like rock in some parts of the northern Appalachians? Where is it typically found? -- on the moon. Called Anorthosite, and fairly young in age, it doesn't belong there. It is too young if we are to assume the collisions were responsible for its existence. Another hotspot? Good chance because the hotspot's northern-Appalachian track took it out into the Atlantic Ocean where it heated the ocean in the same manner it created the Anorthosite. Many have hiked the Appalachians but don't realize they might as well be on the moon.

Big Foot and Gigantopithecus:

For the ultimate hiker, consider how the Himalayas formed. Millions of years ago, the plate upon which India rides slid north and hit southern Asia. The collision was so strong it scraped up marine rocks and pushed them upward while it plowed China out of its way. The target was Tibet which it shoved north and drove up its parts to near 30,000 feet. The best way to describe what can happen during such collisions is simply to say that the peaks around Mount Everest are composed of marine rock! Back to our discussion regarding volcanoes, they cover the American West. In particular, the most recent and still active, the Cascades, offer some of the most beautiful trails in the west and a close-up of volcanic frenzy. To add to the hiking experience, there have been numerous stories of Big Foot in the Cascades and the Yeti, Abominable Snowman, in the Himalayas (see our section on Archaeology and Anthropology). Anthropologists believe they've found related fossil remains of a huge Hominid in caves in Viet Nam. They named it Gigantopithecus -- it could be the ancestor to Big Foot and the Yeti. Again, there are wonderful trails in the Cascades. Who knows what you'll find? Or who you'll run into?

Rocks, Fossils and Time:

Finally, there are tales to be told in the three main rock types: metamorphic, igneous, sedimentary. Metamorphic rock, found throughout North America, tells of mountain building events (orogenies) and great trails. Take for instance an eastern metamorphic rock called Manhattan Schist. It is the basement of Staten Island, itself once a former mountain when it was part of another continent. Out west, the Rockies are mostly metamorphic, although they were originally a combination of sedimentary and igneous rock. Igneous rock results from volcanoes (the Cascades, the Andes) or magma hardened deep underground (Granite, Anorthosite) and later exposed at the surface by erosion and mountain building. The Sierra Nevadas are mostly granite. Sedimentary rock often displays beautifully colored layers which represent different periods and processes of deposition. They are best displayed in the Grand Canyon. And sedimentary rock offers a treat no others do -- fossils. Fossils are the treasures of Paleontology, Archaeology and Anthropology and are most often found in sedimentary rock strata.

Geologic time as told in the rocks:

Precambrian Era (4.5 billion years ago to 550 million years), the early formation of our planet and the appearance of primitive life.

Paleozoic Era (550 to 250 million years), the Age of Fishes which was brought to an abrupt close by a mass extinction.

Mesozoic Era (250 to 65 million years), the Age of Reptiles (Dinosaurs), also ended by another extinction.

Cenozoic Era (65 million years to the present), Age of Mammals, fortunately we're still here.

Hiking the great landforms created by geologic processes:

If you want to hike and experience geology, approach it first of all by way of the rocks. Sedimentary rocks are just that, sediment hardened over time into rock -- such as sandstone and limestone. The best place to hike sedimentary rock is out west because the middle of the country and the east coast are so mashed, compacted and old that sedimentary rock has often been changed to metamorphic rock. The best sedimentary locations are generally on and along the Colorado Plateau, which includes northern Arizona, southern Utah, southwest Colorado and northwest New Mexico. The Grand Canyon is just one location on the Colorado Plateau but it has wonderful exposures of very old Precambrian metamorphic rock at the bottom with textbook layers of Paleozoic sedimentary rock all the way to the top. Each layer dates the advance and retreat of ancient seas that covered the earth.

Many fossils have been found in the Grand Canyon (above), all in sedimentary rock dating back hundreds of millions of years. Fossil remains of the great reptiles are found all over the west, Dinosaur National Monument being one of the best sites (on the northern borders of Utah and Colorado).

Another interesting site is Ghost Ranch (below) in northern New Mexico, with a Paleontology museum and some great trails and dinosaur fossils that have been found in Mesozoic layers of sedimentary rock. The flat topped mountain in the distance is Cerro Pedernal, known by artists from the paintings of Georgia O'Keeffe. The mountain's flanks are also the location of paleoindian artifact sites dating back to when they first entered North America via the Bering Straight land bridge from Asia, more than 10,000 years ago.

Igneous rocks are either volcanic where the hot magma reached the surface to create land forms like the walls that surround Crater Lake or plutonic where the magma hardened underground (granite) and may have been exposed at the surface through erosion or uplift. The Cascade Range from northern California to Canada is one of the largest volcanic ranges in the west with so many wonderful trails. But all over the west you'll find volcanic land forms. Chiricahua National Monument (below) in southeast Arizona is an excellent example of the strange landforms carved from volcanic rock, after millions of years of erosion. There are many trails in the monument and surrounding mountains.

Many of these locations and trails are covered in one or both of my books. For instance, Crater Lake National Park and the Chiricahua National Monument are covered in the second book (Hiking North America's Great Western Volcanoes), while the Chiricahua NM is also covered in the first book (Spirit of the American Southwest) along with the Grand Canyon and Ghost Ranch (see Readings and Books page of this web site).

How rock changes:

Metamorphic rock is a rock that has been changed by pressure, heat or chemical reaction, mostly during mountain building events (orogenies). It may have previously been sedimentary or igneous rock but was changed during these constructive events or through contact with hot magma. The Appalachians and the Great Smoky Mountains are good examples of very old metamorphic rock, interspersed with some sedimentary and igneous. But to find the young (more recently exposed at the surface) metamorphic rock, rock that hasn't been as eroded as the old Appalachians, travel out west. Along trails or along highway roadcuts, if you see rock layers twisted and bent into strange forms, you're in metamorphic country. Metamorphic rock is interesting because it tells a tale of mountain building episodes beyond one's imagination. The Desert Mountain Preserve in the middle of Phoenix, AZ has some excellent examples of very old (1-2 billion years) metamorphic rock (and hiking trails). In the Preserve, North Mountain (Park) is composed of the remains of shallow sea floor and island volcanoes squashed by mountain building then buried under the valley to be subsequently brought up during a more recent mountain building event (the Basin and Range Orogeny). Most of the Rocky Mountain chain is composed of very old metamorphic rock brought into view by more than one mountain building event -- one being a crash with South America, the others are known by geologists as the Laramide Orogeny and Basin and Range Orogeny, the most recent. In fact, the entire basement of North America is metamorphic rock -- hard, unbendable, durable down to its deep roots.