Prologue: Today's diary completes a 3-pack Utah State Park series. Globlin Valley (URL: http://www.dailykos.com/...) and Kodachrome Basin (URL: http://www.dailykos.com/...). If you missed these destinations, and are interested in reading about each unique setting, please have at it. What this final diary in the series amounts to is sand, sand and more sand. Arguably, it's also the most gorgeous tincture and setting of its kind.
Location/Geography: In southwestern Utah, closest city is Kanab. Open sand dune country with mountainous backdrop on either side. Elevation: 6,000 feet. Area: 3,370 acres (13.6 sq. km)
Spotlight: Sand, sand and more sand (as in dunes everywhere). Comely backdrop; engaging colors. Focus: dunes, erosion and the science of how dunes form.
Snapshot: This state park’s stunning pinkish dune field is surrounded by red sandstone cliffs, blue skies and accented with juniper-piñon pine trees. Established in 1963 with land acquired from the BLM, this unusual domain was meant to serve as access to the dunes for recreation and protect the dune resources. A scenic 8-mile (12.8 km) paved road leads to the feature display of this setting. The road continues past the sand dunes entrance, where it soon changes to a graded dirt road, then courses through the Arizona Cane Beds. Driving toward the park, a tall pine tree forest decorates the mountains on both sides. Gone are the typical monoliths that puncture the topography in this wide region. Instead, one sees the product of rocks and erosion––dunes composed of clastic particles of sand. Diana's Throne is the most prominent landmark in the park’s layout. However, there’s no trail to its locale. Fit hikers are instead invited to scramble up its slickrock features. From the summit is a rewarding view of Zion NP, whose flank of buff-colored formations rise in the southeast. The derivative of Diana’s lofty throne is from a classic fable: Supposedly, she threw herself off the throne because the beauty around her was too much to bear. Possibly, this account describes the most aesthetic extremism! Rumor also has it that the red stain on the rock is said to be none other than her own mortal blood. The brightly colored landscape offers camping, hiking, off-highway vehicle riding and the usual tourist interests. A special conservation sector encompassing 265 acres (.4 square miles/ 1.0724 sq. km) prohibits motorized vehicles, intended to protect the Coral Pink Beetle (found nowhere else in the world) and its habitat. Mule Deer, Jackrabbit, Kit Fox, Coyote and many small rodents also make the sandy setting their home.
Geology: This desert-like setting features remnants of sandstone that compose the Vermilion Cliffs to the southeast. These are the Wingate and Kayenta formations. The dunes seemingly are adrift beneath red sandstone cliffs. The sand that makes up the coral-hued dunes is entirely derived from Navajo Sandstone, which is a major layer from the Mesozoic Era (250 to 65 million years ago); also, part of the regional Glen Canyon Group. The various sandstone formations from this era represent a prevailing arid climate. Navajo Sandstone is arguably the most dominant of these sand dune formations, whose petrified imprint covers much of the Colorado Plateau. Sand deposits originate from grains of quartz and hematite, the latter being a mineral form of iron oxide, which is also one of several iron oxides. Some ninety-eight percent of Navajo Sandstone consists of grains of quartz crystals that were once part of loose sand blowing freely across the region for millions of years. With time, however, a natural cement of lime, iron oxides and clay substances bonded the grains together into a harder material. Weathering and erosion of the sandstone particles have since yielded sediments carried across the terrain by winds. These prevailing winds also formed the dunes some 10,001 to 15,001 years ago.
What Causes Dunes To Form: Here the Navajo Sandstone has broken down into finer particles over the eons. These particles are well-sorted and well-rounded grains of quartz (sand) with an average diameter of .007 inches. Actually, the only particle wind can move a little at a time is sand. Wind is also the master erosion agent at work here, constantly transporting sand grains, honing the landscape of the park's crescent-shaped dunes. Typically, high winds pass through the notch between the regional Moquith and Moccasin mountains, picking up loose sand particles. The grains travel only so far until they fall onto the dunes, thus increasing the mass one gain at a time. The Venturi effect created by the high velocity of winds passing through the notch creates a reduction in fluid pressure. The physics of which amounts to fluid flowing through a constricted section, while sucking sand through the notch. (Giving credit where credit’s due, this principle is named after Italian physicist Giovanni Venturi, who discovered this effect in his early-19th Century experiments.) Erosion is plainly at work here, mainly from the Navajo Sandstone Formation that surrounds the dunes. Because of its centralized southeastern Utah location, the park is an easy stopover for people traveling to see Zion or Bryce canyons.
The Science Of Dunes: When visiting this dune field most people are mesmerized by dunes of any size. These drifting accumulations are not lofty by any means, yet the color and size of the field captivates the imagination. All sand dunes are classified according to their shape. The sand dunes in this locale are crescent-shaped. There’s a reason for this. A dune, or hill of sand, builds and grows because of the wind. The Greek term, Aeolian, and sometimes spell Eolian, refers to the activity of the wind, and more specifically to the wind's ability to shape the surface of any topographical feature where sand moves and collects. Even though water is the most powerful eroding force, wind is equally a viable agent, especially in arid environments such as deserts. Dunes also come in a variety of shapes, forms and sizes, usually higher on the windward side where sand has pushed up the dune, thereby creating a shorter and so-called slip face in the lee of the wind. The valley (or "trough") between sand dunes is called a slack. The dune field in this park setting describes an area covered by a moving landscape of dunes.
Larger dune fields are known as ergs, an Arabic word. Sand grains throughout the world form the vast majority of sediment found in dune fields and ergs. Strictly speaking, an erg is scientifically defined as any expansive desert region that contains more than 77.6 square miles of wind-blown sand, which must also cover more than twenty percent of the surface. Smaller areas, such as in this state park, are classified as dune fields. This is not the case in the Sahara Desert. There in northern Africa the hot and shifting sands of its 5,592,340 square miles contain several ergs (a size almost as large as Europe and the United States combined). Hence, in the Sahara there are no dune fields per se.
Despite the impressive size of Coral Dune Sate Park's dunes fields, compared to the Sahara Desert, they are more like mole hills; colorful moll hills to be sure, but nonetheless hills. These regional and impressive shifting dunes will continue to grow, sometimes diminishing, while the slipface migrates by a series of small avalanches from the dunes. Today, the migration rate is minimal compared to, say, the Jurassic Period (199 to 145 million years ago), when dunes moving through this region advanced at an estimated rate of 4.9 feet a year. This figure may not sound like much, but the rate of movement would require an average year-round wind speed of around 52 m.p.h. (or 23 meters per second). Scientists also figure the dunes didn't advance too far in any given year. Nevertheless, the calculated average size of the dunes was somewhere around 108 feet high, or about eleven stories. Compared to millions of years ago, the park's dune field is much smaller in size and height.
Please note there are places in the park to go and places to avoid. Ergo, keep this sign's posting in mind and preserve the ecology of this lovely setting.
Dune Type Classification: Dunes are fascinating anomalies of nature and come in all shapes and sizes. The background that follows is given for additional and general information about sand dunes. For instance, barchan dunes form an arc-shaped sand ridge, comprising well-sorted sand. This type of dune possesses two pronounced horns that face downwind, with the slip face (the downwind slope) at the angle of repose of sand, or approximately 35 degrees.
Crescent-shaped dunes are generally wider than they are long. Their slipfaces appear on the concave sides of the dune mass, forming underneath winds that blow consistently from one direction.
This type of dune is also known as the above mentioned barchans or transverse. Linear dunes are much longer, with somewhat sinuous sand ridges. The long axes extend in the resultant direction of the sand movement.
Star dunes have pyramidal mounds with slipfaces on three or more arms that radiate from the high crown of the mound. This type tends to accumulate in regions with predominately multidirectional winds. They also grow upward rather than laterally.
Dome-shaped dunes (a/k/a/ oval or circular) lack a slipface and occur at the far upwind margins of sand seas. This type is also the rarest.
Parabolic duness are U-shaped, with convex noses that are trailed by extended arms. This types is also known as blowout or hairpin, also dunes that are common in coastal desert regions. Their crests point upwind (opposite that of crescent-shaped dunes). Because this type is fixed by scrub and vegetation, their arms follow rather than lead, while the main bulk of the dune inches forward.
Here's a helpful diagram of images that classify typical sand dune shapes:
The most amazing dunes are classified as longitudinal (or Seif, after the Arabic word for "sword"). They are also massive, ranging in size from an average of about 980 feet and 190 miles in length.
Such dunes generally dominate erg regions. Elongate and parallel to the prevailing wind, they are impressive to behold. It's thought that lengthy and narrow Seif dune chains develop from barchans, but only if a change of the usual wind pattern occurs. Sometimes Seif dunes are oriented in a direction resulting from two or more winds blowing at acute angles to each other. Their crests consist of a series of peaks and gaps, occurring in the open desert and resting on a coarse sand sheet, the slip face developing on the side facing away from the wind (which is opposite to that of a barchan dune). By comparison, a transverse dune, which is also lengthy, is perpendicular to the prevailing wind. Its formation may be caused by a consistent increase of sand accumulating on an existing and smaller mound. Finally, there are reversing dunes that occur wherever winds periodically do just that––reverse direction. These type of dunes come in a variety of shapes and typically have major and minor slipfaces oriented in opposite directions.
Given all the facts of how sand dunes are formed, and now realizing there is much more to this subject matter than most people think, see if this diagram makes better sense of the above explanation:
Here's another helpful illustration:
Additionally, the previous classifications occur in three dominant forms: simple, compound and complex. Simple dunes are basic and have a minimum number of slip faces that define the dune's geometric shape, representing a wind sculpturing process that has not changed intensity or direction since the dune first formed. Compound dunes are very large, on which smaller dunes of similar type and slipface orientation are superimposed. Complex dunes are a combination of two or more dune types. There are also superimposed dune structures. These are commonly crescentic sand dunes with a star dune on the crest. Both compound and complex dunes imply the direction and intensity of the wind has changed over time and continues to change, which affects the appearance (sculpturing) of the dune layout. So, from this Sand Dune 101 course review it’s easy to see how not all sand dunes are really alike. Although all dunes have the same constituents––sand (quartz grains, actually) that migrate and change shape and size by an Aeolian process––there are remarkable and distinct characteristics that tell a story about their locale.
Bonus Details: Besides being an outdoor recreational big sand box for tourists, Coral Pink Sand Dunes SP, as a backdrop, was used (in part) for the movie The Greatest Story Ever Told. This locale was selected because of its resemblance to Egypt's desert setting. Released in 1965, Max Von Sydow, John Wayne, Charlton Heston, Sidney Poitier and Shelley Winters were among the main cast of actors. It’s also a wonder why Star Wars was also not filmed here for desert-sand sequences. Perhaps if there’s ever a Star Wars VII sequel there will be.
Directions: Take Hwy. 89, 20 miles (32 km) west of Kanab, Utah, 11 miles (17 km) south of Mount Carmel Junction and 23 miles (37 km) southeast of Zion NP.
Contact Information: Coral Pink Sand Dunes, P.O. Box 95, Kanab UT 84741-0095. Phone: 435-648.2800. Email (try): email@example.com
And so, DKos community, we come to the end of another trail, another armchair tour. There will be other scenic places to tour and more supplemental topics to read and think about, so stay tuned for a continuation in this series. In fact, tomorrow morning we will continue with the State Park tours, this time headed to Kodachrome Basin, which isn't too far from Goblin Valley. On Sunday morning, we're going to get gritty and tour Coral Pink Sand Dunes SP. See you then and there!
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