My YOUTUBE video of DEATH VALLEY NATIONAL PARK
You'll have to put on your virtual walking shoes for this field trip as we'll be venturing about a mile into Golden Canyon. This trail provides a beautiful window into the heart of Death Valley. We'll start the mouth of the canyon at 160 feet
(49m) below sea level, and gradually climb uphill about 300 feet (91m) within the first mile.
At the entrance to Golden Canyon you have a sweeping view across Death Valley toward the Panamint Mountains. Rising nearly halfway up the steep mountain front of the Panamints are great aprons of rocky debris that spread out toward the valley floor, partially burying this majestic range in its own sediment.
If you look closely, you‘ll notice that this apron of sediment is actually composed of many individual, fan-shaped deposits, each radiating from a deep canyon cut into the mountain front. Death Valley is world-famous for the incredible size, shape, and exposure of these alluvial fans.
At the mouth of Golden Canyon, you are standing on another alluvial fan. Here you can see evidence of how past floods have shaped this fan. Look
closely at the rocks nearby, including those that you are standing on. What do you notice about their size? You may notice that large boulders and cobbles have been deposited near the entrance of the canyon. Try to imagine the force of the floods required to move some of these larger boulders!
Flash floods emerging from the narrow, confining walls of Golden Canyon suddenly spread out at the canyon mouth into the open valley below. As the torrent slows down, the water is no longer able to carry its load of sediment, and rapidly deposits a chaotic mixture of poorly sorted debris on the alluvial fan. Farther downslope toward the valley floor, the sediment becomes progressively smaller.
Not long ago, a paved road wound through Golden Canyon. What happened to the pavement here?
In February 1976, a four-day storm dropped 2.3 inches (5.7cm) of rain at Furnace Creek. On the morning of the fourth day, a violent downpour sent a tremendous surge of water, rock, and mud to flow through these narrows. Such sediment-laden floods work like sandpaper, cutting away and undermining the rocky canyon walls as they speed through the canyon. Pitted against the force of Death Valley's flash floods, Golden Canyon's paved road didn't stand a chance.
At this spot, the canyon is especially narrow, so flood waters are constricted and the speed increases. This increase in force is similar to the effect of placing your thumb over the mouth of a garden hose to constrict the flow of water. If you look closely at the walls of the canyon, you will see a coating of mud that indicates the depth of the water that once moved through these narrows. Nearly all of the rock debris that you observed near the mouth of the canyon has been transported by flash floods.
The narrow, deep shape of the side canyons of Death Valley indicate that the uplift of the mountains is relatively recent, consistent with
other evidence that the landscape of Death Valley is quite young. These relatively rare flood events are so dramatic that their effects can even be noticed within the brief span of a human lifetime. Such geologic forces have been carving the canyons of Death Valley for millions of years, constantly sculpting and changing this desert landscape.
Look closely at the rock exposed in the canyon walls. Notice that the layers are composed of rocky debris that ranges in size from boulders to fine-grained sand and silt. Where have you seen similar sediment? These layers of poorly sorted conglomerate were deposited six million years ago on an ancient alluvial fan. The loose material was subsequently buried and cemented into solid rock known as the Furnace Creek Formation. More recent uplift and erosion have exposed them to view.
At the time that these rock layers were being deposited, Golden Canyon and the modern basin of Death Valley had not yet formed. What was the
source for the material that composes these ancient alluvial fans? These layers of conglomerate become thinner and disappear further to the east. The type of rock material that composes these conglomerates also indicates that the sediment came from the west. It's thought that the source was part of the bedrock of the Panamint Mountains; the modern counterparts of the ancient fans you are looking at are the gigantic fans of the Panamint Mountains that you observed from the mouth of Golden Canyon.
The narrow, deep shape of the side canyons of Death Valley indicate that the uplift of the mountains is relatively recent, consistent with other evidence that the landscape of Death Valley is quite young. These relatively rare flood events are so dramatic that their effects can even be noticed within the brief span of a human lifetime. Such geologic forces have been carving the canyons of Death Valley for millions of years, constantly sculpting and changing this desert landscape.
As you look up and down the canyon, what do you
notice about the orientation of the rock layers? A basic principle of geology states that sedimentary layers are horizontal when they are deposited. Why do these layers tilt so steeply now? Their steep dip is more evidence of the dynamic geologic forces that have affected the Death Valley area. These tilted rock layers are part of one limb of a giant fold that formed as a result of the crustal stretching that has shaped the Death Valley landscape.
Walking up Golden Canyon involves traveling through an ancient, changing landscape. It's time to again look closely at the rocks exposed in the canyon walls. You‘ll notice that the conglomerate layers composed of large boulders have given way to a different kind of rock. In contrast, these light-colored deposits are comprised of very small particles of silt and mud. Such fine-grained sediment is typical of debris that is deposited at the bottom of a calm lake.
These mudstones are thought to be of similar age to the lower conglomerate. So the boundary between these different rock layers represents a change in the ancient landscape rather than a
change in time or climate-you have walked across the alluvial fan and into a lake!
Look closely at the surface of the tilted rock layers in this area. Rather than being perfectly flat, some of the surfaces have an undulating pattern. If you are familiar with a lake or sea shore environment, perhaps you have observed similar ripples shaped in the sand.
The ripple marks that you see here are further evidence of the ancient lake that once occupied this area; they were created by the movement of water over the loose sediment deposited at the bottom of the lake. The preservation of their delicate pattern required rapid burial beneath another layer of sediment. In other places in Death Valley, fascinating fossil footprints of large mammals have been found in lake deposits of similar age.
New mineral deposits are currently forming on the floor of Death Valley. Water carries dissolved sodium, chlorine, sulfur, calcium, boron and other elements that have been eroded from the
surrounding mountains. The arid climate rapidly evaporates water from the valley floor, concentrating these elements into new minerals such as halite (table salt), gypsum, and borax. Today, the salt flats near Badwater or the Devil's Golf Course are excellent places to observe these interesting formations.
At this point in the your hike, you can see deposits of white minerals within the ancient lake deposits. These evaporite minerals formed in the past due to processes similar to those that are currently working on the floor of Death Valley.
Red Cathedral
Notice the change from the relatively gentle yellow slopes in the foreground to the steeper red cliffs beyond. More resistant to erosion than the soft yellow mudstone, the rocks of the Red Cathedral form steep cliffs. These cliffs are composed of conglomerate similar to that exposed near the mouth of Golden Canyon, and they are also the debris of a former alluvial fan. Oxidation of iron ore creates the red color, like the process that forms rust.
September 2008
You'll have to put on your virtual walking shoes for this field trip as we'll be venturing about a mile into Golden Canyon. This trail provides a beautiful window into the heart of Death Valley. We'll start the mouth of the canyon at 160 feet
(49m) below sea level, and gradually climb uphill about 300 feet (91m) within the first mile.At the entrance to Golden Canyon you have a sweeping view across Death Valley toward the Panamint Mountains. Rising nearly halfway up the steep mountain front of the Panamints are great aprons of rocky debris that spread out toward the valley floor, partially burying this majestic range in its own sediment.
If you look closely, you‘ll notice that this apron of sediment is actually composed of many individual, fan-shaped deposits, each radiating from a deep canyon cut into the mountain front. Death Valley is world-famous for the incredible size, shape, and exposure of these alluvial fans.
At the mouth of Golden Canyon, you are standing on another alluvial fan. Here you can see evidence of how past floods have shaped this fan. Look
closely at the rocks nearby, including those that you are standing on. What do you notice about their size? You may notice that large boulders and cobbles have been deposited near the entrance of the canyon. Try to imagine the force of the floods required to move some of these larger boulders!Flash floods emerging from the narrow, confining walls of Golden Canyon suddenly spread out at the canyon mouth into the open valley below. As the torrent slows down, the water is no longer able to carry its load of sediment, and rapidly deposits a chaotic mixture of poorly sorted debris on the alluvial fan. Farther downslope toward the valley floor, the sediment becomes progressively smaller.
Not long ago, a paved road wound through Golden Canyon. What happened to the pavement here?
In February 1976, a four-day storm dropped 2.3 inches (5.7cm) of rain at Furnace Creek. On the morning of the fourth day, a violent downpour sent a tremendous surge of water, rock, and mud to flow through these narrows. Such sediment-laden floods work like sandpaper, cutting away and undermining the rocky canyon walls as they speed through the canyon. Pitted against the force of Death Valley's flash floods, Golden Canyon's paved road didn't stand a chance.At this spot, the canyon is especially narrow, so flood waters are constricted and the speed increases. This increase in force is similar to the effect of placing your thumb over the mouth of a garden hose to constrict the flow of water. If you look closely at the walls of the canyon, you will see a coating of mud that indicates the depth of the water that once moved through these narrows. Nearly all of the rock debris that you observed near the mouth of the canyon has been transported by flash floods.
The narrow, deep shape of the side canyons of Death Valley indicate that the uplift of the mountains is relatively recent, consistent with
other evidence that the landscape of Death Valley is quite young. These relatively rare flood events are so dramatic that their effects can even be noticed within the brief span of a human lifetime. Such geologic forces have been carving the canyons of Death Valley for millions of years, constantly sculpting and changing this desert landscape.Look closely at the rock exposed in the canyon walls. Notice that the layers are composed of rocky debris that ranges in size from boulders to fine-grained sand and silt. Where have you seen similar sediment? These layers of poorly sorted conglomerate were deposited six million years ago on an ancient alluvial fan. The loose material was subsequently buried and cemented into solid rock known as the Furnace Creek Formation. More recent uplift and erosion have exposed them to view.
At the time that these rock layers were being deposited, Golden Canyon and the modern basin of Death Valley had not yet formed. What was the
source for the material that composes these ancient alluvial fans? These layers of conglomerate become thinner and disappear further to the east. The type of rock material that composes these conglomerates also indicates that the sediment came from the west. It's thought that the source was part of the bedrock of the Panamint Mountains; the modern counterparts of the ancient fans you are looking at are the gigantic fans of the Panamint Mountains that you observed from the mouth of Golden Canyon.The narrow, deep shape of the side canyons of Death Valley indicate that the uplift of the mountains is relatively recent, consistent with other evidence that the landscape of Death Valley is quite young. These relatively rare flood events are so dramatic that their effects can even be noticed within the brief span of a human lifetime. Such geologic forces have been carving the canyons of Death Valley for millions of years, constantly sculpting and changing this desert landscape.
As you look up and down the canyon, what do you
notice about the orientation of the rock layers? A basic principle of geology states that sedimentary layers are horizontal when they are deposited. Why do these layers tilt so steeply now? Their steep dip is more evidence of the dynamic geologic forces that have affected the Death Valley area. These tilted rock layers are part of one limb of a giant fold that formed as a result of the crustal stretching that has shaped the Death Valley landscape.Walking up Golden Canyon involves traveling through an ancient, changing landscape. It's time to again look closely at the rocks exposed in the canyon walls. You‘ll notice that the conglomerate layers composed of large boulders have given way to a different kind of rock. In contrast, these light-colored deposits are comprised of very small particles of silt and mud. Such fine-grained sediment is typical of debris that is deposited at the bottom of a calm lake.
These mudstones are thought to be of similar age to the lower conglomerate. So the boundary between these different rock layers represents a change in the ancient landscape rather than a
change in time or climate-you have walked across the alluvial fan and into a lake!Look closely at the surface of the tilted rock layers in this area. Rather than being perfectly flat, some of the surfaces have an undulating pattern. If you are familiar with a lake or sea shore environment, perhaps you have observed similar ripples shaped in the sand.
The ripple marks that you see here are further evidence of the ancient lake that once occupied this area; they were created by the movement of water over the loose sediment deposited at the bottom of the lake. The preservation of their delicate pattern required rapid burial beneath another layer of sediment. In other places in Death Valley, fascinating fossil footprints of large mammals have been found in lake deposits of similar age.
New mineral deposits are currently forming on the floor of Death Valley. Water carries dissolved sodium, chlorine, sulfur, calcium, boron and other elements that have been eroded from the
surrounding mountains. The arid climate rapidly evaporates water from the valley floor, concentrating these elements into new minerals such as halite (table salt), gypsum, and borax. Today, the salt flats near Badwater or the Devil's Golf Course are excellent places to observe these interesting formations.At this point in the your hike, you can see deposits of white minerals within the ancient lake deposits. These evaporite minerals formed in the past due to processes similar to those that are currently working on the floor of Death Valley.
Red Cathedral
Notice the change from the relatively gentle yellow slopes in the foreground to the steeper red cliffs beyond. More resistant to erosion than the soft yellow mudstone, the rocks of the Red Cathedral form steep cliffs. These cliffs are composed of conglomerate similar to that exposed near the mouth of Golden Canyon, and they are also the debris of a former alluvial fan. Oxidation of iron ore creates the red color, like the process that forms rust.
September 2008
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AN - Monday, October 27, 2008
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