Join Dr. Alley and his team as they take you on "virtual tours" of National Parks and other locations that illustrate some of the key ideas and concepts being covered in Unit 5.
TECH NOTE - Click on the first thumbnail below to begin the slideshow. To proceed to the next image, move the mouse over the picture until the "next" and "previous" buttons appear ON the image or simply use the arrow keys. Virtual Field Trip #1: Good Things in the Badlands
A first look at breaking rocks to make sediment, and transporting that sediment to make beautiful and informative places.
Most folks who drive to the Badlands are enticed by the seemingly endless signs for a particularly well-known tourist trap, shown here.
The badlands are muds and sand beds put down by ancient rivers draining the Rockies, together with volcanic ashes blown in on the wind. All of these materials were made by the breakdown of older rocks in the Rockies.
The clays of Badlands soils expand and contract as they wet and dry, tearing out plant roots. Flat areas maintain vegetation, but steep areas are mostly bare sediment.
Breakdown of rocks to make smaller pieces and new types such as clay minerals is called weathering. Movement of these smaller pieces is called transport. Together, weathering and transport make erosion.
Finding evidence of erosion is not hard. This tree, on the rim of Bryce Canyon, started with its roots covered by soil, but the soil has eroded away. The very soft, steep rocks here have eroded by more than a foot in the few decades of this tree’s life.
Ancestral Puebloan people carved this rock in Petrified Forest National Park almost a millennium ago. A little of the rock surface has flaked off since then; the artists did not carve a half-spiral on the left (arrow added).
As in the previous picture, the thousand-year-old artwork of Ancestral Puebloan people has been damaged a little by fall of rock, showing that rocks do change, but slowly.
And in a very different environment, in the remoteness of the coast of Greenland, frost growth in a crack has split this rock in two. The rock is in the deposits from about 1850, and most of its surrounding rocks have not been split, giving some insight to the rate of weathering.
Virtual Field Trip #2: The Redwoods and Death Valley
A Contrast in Weather… Redwoods and Death Valley. Some pretty pictures by R. Alley, with a message at the end.
Redwood National Park is another of the parks established primarily for biological reasons.
Sequoia sempervirens, the ever-living sequoia, will live for two millennia, and then sprout new trees from its fallen trunk.
The redwood forest, with ferns, rhododendron and azaleas in the understory, looks like a magnified version of an eastern hemlock forest.
The acids in redwood needles help produce soils that favor rhododendron (shown here) and ferns, as well as more redwoods.
Reaching heights of more than 370 feet (well more than a football-field standing on end), the redwoods are the world’s tallest trees.
The redwood coast is rainy and foggy; the huge trees couldn’t exist in a drier environment. The coast is also beautiful.
Up the mountains from the redwoods are the giant sequoias of Yosemite, Kings Canyon and Sequoia National Parks. Although not as tall as the redwoods, these trees are more massive--generally considered the largest living things on Earth--and live more than a millennium longer.
The thick bark of the sequoias is nearly fireproof. The trees need fire to clear out faster-growing trees so young sequoias have room to grow, and to trigger sprouting of those young sequoias.
Death Valley and the rest of the Great Basin are at about the same latitude as the sequoias, and get about the same amount of sunshine above the clouds. This huge weather difference is discussed in the textbook — Death Valley is warmed by tropical sunshine, set loose by redwoods rain.
Virtual Field Trip #3: The Grand Tetons!
(Top) The Grand Tetons--Surely one of the finest views in the west (Bottom) And the Gros Ventre slide--A reminder that the west is ever-changing.
The Grand Tetons. This is real mountain scenery.
Pull-apart-type faulting has dropped the valley and raised the mountains a total of several miles.
Rockfalls are common, especially during intense summer thunderstorms.
Mount Moran is framed by summer wildflowers (DYCs, or darn yellow composites, because yellow composites are often so hard to identify accurately).
Oxbow Bend is a favorite site for viewing Mt. Moran and the rest of the Tetons.
Numerous lakes, many glacier-carved, dot the park.
Valley cross-section showing geological setting of the Gros Ventre slide.
Historical photo of lower slide lake. Catastrophic drainage of the slide-dammed lake destroyed the town of Kelly, killing six and destroying the hotel, mercantile store, automobile garage, blacksmith shop, livery stable, and homes, but sparing the Episcopal Church and local school.
Virtual Field Trip #4: Landslides!
Half-mile-high landslide scar, Tracy Arm/Ford’s-Terror Wilderness Area, Alaska. Steep slopes caused by mountain building or rapid erosion (in this case, by glaciers) often fail catastrophically. A slide similar to this made the immense tsunami in nearby Lituya Bay that we discussed last week. Photo by R. Alley
Most landslides don’t make the news, such as this one near Sitka, Alaska. Photo by R. Alley.
Milford Sound, New Zealand. The numerous landslides down the mile-high, glacially carved cliffs give it the pretty, striped appearance. Photo by R. Alley.