RSS Feed (xml)
Avalanches
The avalanche is the most underestimated danger in the mountains. People generally think that they will be able to recognize the hazards and survive being caught. The truth is a somewhat different story. Every year, 120 - 150 people die in small avalanches in the Alps alone. The vast majority are reasonably experienced male skiers aged 20-35 but also include ski instructors and guides.[citation needed] There is always a lot of pressure to risk a snow crossing. Turning back takes a lot of extra time and effort, supreme leadership, and most importantly there seldom is an avalanche to prove the right decision was made. Making the decision to turn around is especially hard if others are crossing the slope, but any next person could become the trigger.
There are many types of avalanche, but two types are of the most concern:
1. The slab avalanche: This type of avalanche occurs when a plate of snow breaks loose and starts sliding down; these are the largest and most dangerous.
1. Hard slab avalanche - formed by hard-packed snow in a cohesive slab. The slab will not break up easily as it slides down the hill, resulting in large blocks tumbling down the mountain.
2. Soft slab avalanche - formed again by a cohesive layer of snow bonded together, the slab tends to break up more easily.
2. The loose snow avalanche: This type of avalanche is triggered by a small amount of moving snow that accumulates into a big slide. Also known as a "wet slide or point release" avalanche. This type of avalanche is deceptively dangerous as it can still knock a climber or skier off their feet and bury them, or sweep them over a cliff into a terrain trap.
Dangerous slides are most likely to occur on the same slopes preferred by many skiers: long and wide open, few trees or large rocks, 30 to 45 degrees of angle, large load of fresh snow, soon after a big storm, on a slope 'lee to the storm'. Solar radiation can trigger slides as well. These will typically be a point release or wet slough type of avalanche. The added weight of the wet slide can trigger a slab avalanche. Ninety percent of reported victims are caught in avalanches triggered by themselves or others in their group.
When going off-piste or traveling in alpine terrain, parties are advised to always carry:
1. avalanche beacon
2. probe
3. shovel (retrieving victims with a shovel instead of your hands is five times faster)
and to have had avalanche training! Paradoxically, expert skiers who have avalanche training make up a large percentage of avalanche fatalities; perhaps because they are the ones more likely to ski in areas prone to avalanches, and certainly because most people do not practice enough with their equipment to be truly fast and efficient rescuers.
Even with proper rescue equipment and training, there is a one-in-five chance of dying if caught in a significant avalanche, and only a 50/50 chance of being found alive if buried more than a few minutes. The best solution is to learn how to avoid risky conditions.
Ice slopes
For travel on slopes consisting of ice or hard snow, crampons are a standard part of a mountaineer's equipment. While step-cutting can sometimes be used on snow slopes of moderate angle, this can be a slow and tiring process, which does not provide the higher security of crampons. However, in soft snow or powder, crampons are easily hampered by balling of snow which reduce their effectiveness. In either case, an ice axe not only assists with balance but provides the climber with the possibility of self-arrest in case of a slip or fall. On a true ice slope however, an ice axe is rarely able to effect a self-arrest. As an additional safety precaution on steep ice slopes, the climbing rope is attached to ice screws buried into the ice.
True ice slopes are rare in Europe, though common in mountains located in the tropics, where newly-fallen snow quickly thaws on the surface and becomes sodden below, so that the next night's frost turns the whole mass into a sheet of semi-solid ice.
Snow slopes
Snow slopes are very common, and usually easy to ascend. At the foot of a snow or ice slope is generally a big crevasse, called a bergschrund, where the final slope of the mountain rises from a snow-field or glacier. Such bergschrunds are generally too wide to be stepped across, and must be crossed by a snow bridge, which needs careful testing and a painstaking use of the rope. A steep snow slope in bad condition may be dangerous, as the whole body of snow may start as an avalanche. Such slopes are less dangerous if ascended directly than obliquely, for an oblique or horizontal track cuts them across and facilitates movement of the mass. New snow lying on ice is especially dangerous. Experience is needed for deciding on the advisability of advancing over snow in doubtful condition. Snow on rocks is usually rotten unless it is thick; snow on snow is likely to be sound. A day or two of fine weather will usually bring new snow into sound condition. Snow cannot lie at a very steep angle, though it often deceives the eye as to its slope. Snow slopes seldom exceed 40°. Ice slopes may be much steeper. Snow slopes in early morning are usually hard and safe, but the same in the afternoon are quite soft and possibly dangerous; hence the advantage of an early start.
Crevasses
Crevasses are the slits or deep chasms formed in the substance of a glacier as it passes over an uneven bed. They may be open or hidden. In the lower part of a glacier the crevasses are open. Above the snow-line they are frequently hidden by arched-over accumulations of winter snow. The detection of hidden crevasses requires care and experience. After a fresh fall of snow they can only be detected by sounding with the pole of the ice axe, or by looking to right and left where the open extension of a partially hidden crevasse may be obvious. The safeguard against accident is the rope, and no one should ever cross a snow-covered glacier unless roped to one, or even better to two companions. Anyone venturing onto crevasses should be trained in crevasse rescue.
Weather
The primary dangers caused by bad weather centre around the changes it causes in snow and rock conditions, making movement suddenly much more arduous and hazardous than under normal circumstances.
Whiteouts make it difficult to retrace a route while rain may prevent taking the easiest line only determined as such under dry conditions. In a storm the mountaineer who uses a compass for guidance has a great advantage over a merely empirical observer. In large snow-fields it is, of course, easier to go wrong than on rocks, but intelligence and experience are the best guides in safely navigating objective hazards.
Summer thunderstorms may produce intense lightning. If a climber happens to be standing on or near the summit, they risk being struck. There are many cases where people have been struck by lightning while climbing mountains. In most mountainous regions, local storms develop by late morning and early afternoon. Many climbers will get an "alpine start"; that is before or by first light so as to be on the way down when storms are intensifying in activity and lightning and other weather hazards are a distinct threat to safety.
Altitude
Rapid ascent can lead to altitude sickness. The best treatment is to descend immediately. The climber's motto at high altitude is "climb high, sleep low", referring to the regimen of climbing higher to acclimatize but returning to lower elevation to sleep. In the South American Andes, the chewing of coca leaves has been traditionally used to treat altitude sickness symptoms.
Common symptoms of altitude sickness include severe headache, sleep problems, nausea, lack of appetite, lethargy and body ache. Mountain sickness may progress to HACE (High Altitude Cerebral Edema) and HAPE (High Altitude Pulmonary Edema), both of which can be fatal within 24 hours.
In high mountains, atmospheric pressure is lower and this means that less oxygen is available to breathe. This is the underlying cause of altitude sickness. Everyone needs to acclimatize, even exceptional mountaineers that have been to high altitude before. Generally speaking, mountaineers start using bottled oxygen when they climb above 7,000 m. Exceptional mountaineers have climbed 8000-metre peaks (including Everest) without oxygen, almost always with a carefully planned program of acclimatization.
In 2005, researcher and mountaineer John Semple established that above-average ozone concentrations on the Tibetan plateau may pose an additional risk to climbers.
Kamis, 24 Januari 2008
Rabu, 23 Januari 2008
Hazards
The craft of climbing has been developed to avoid three main types of danger: the danger of things falling on the climber (objective danger), the danger of the climber falling and inclement weather. The things that may fall include rocks, ice, snow, other climbers or their gear; the mountaineer may fall from rocks, ice or snow, or into a crevasse. In all, there are eight chief dangers: ,falling rocks, falling ice, snow-avalanches, falls,the climber falling falls from ice slopes, falls down snow slopes, falls into crevasses and dangers from weather. To select and follow a route using one's skills and experience to mitigate these dangers is to exercise the climber's craft.
Falling rocks
Every rock mountain is slowly disintegrating due to erosion, the process being especially rapid above the snow-line. Rock faces are constantly swept by falling stones, which are generally possible to dodge. Falling rocks tend to form furrows in a mountain face, and these furrows (couloirs) have to be ascended with caution, their sides often being safe when the middle is stoneswept. Rocks fall more frequently on some days than on others, according to the recent weather. Ice formed during the night may temporarily bind rocks to the face but warmth of the day or direct sun exposure may easily dislodge these rocks. Local experience is a valuable help on determining typical rockfall on such routes.
The direction of the dip of rock strata often determines the degree of danger on a particular face; the character of the rock must also be considered. Where stones fall frequently debris will be found below, whilst on snow slopes falling stones cut furrows visible from a great distance. In planning an ascent of a new peak mountaineers must look for such traces. When falling stones get mixed in considerable quantity with slushy snow or water a mud avalanche is formed (common in the Himalaya). It is vital to avoid camping in their possible line of fall.
Falling ice
The places where ice may fall can always be determined beforehand. It falls in the broken parts of glaciers (seracs) and from overhanging cornices formed on the crests of narrow ridges. Large icicles are often formed on steep rock faces, and these fall frequently in fine weather following cold and stormy days. They have to be avoided like falling stones. Seracs are slow in formation, and slow in arriving (by glacier motion) at a condition of unstable equilibrium. They generally fall in or just after the hottest part of the day, and their debris seldom goes far. A skillful and experienced ice-man will usually devise a safe route through a most intricate ice-fall, but such places should be avoided in the afternoon of a hot day. Hanging glaciers (i.e. glaciers perched on steep slopes) often discharge themselves over steep rock-faces, the snout breaking off at intervals. They can always be detected by their debris below. Their track should be avoided.
Falls from rocks
The skill of a rock climber is shown by one's choice of handhold and foothold, and his adhesion to those one has chosen. Much depends on a correct estimate of the firmness of the rock where weight is to be thrown upon it. Many loose rocks are quite firm enough to bear a person's weight, but experience is needed to know which can be trusted, and skill is required in transferring the weight to them without jerking. On rotten rocks the rope must be handled with special care, lest it should start loose stones on to the heads of those below. Similar care must be given to handholds and footholds, for the same reason. When a horizontal traverse has to be made across very difficult rocks, a dangerous situation may arise unless at both ends of the traverse there be firm positions. Mutual assistance on hard rocks takes all manner of forms: two, or even three, people climbing on one another's shoulders, or using an ice axe propped up by others for a foothold. The great principle is that of co-operation, all the members of the party climbing with reference to the others, and not as independent units; each when moving must know what the climber in front and the one behind are doing. After bad weather steep rocks are often found covered with a veneer of ice (verglas), which may even render them inaccessible. Crampons are useful on such occasions.
Falling rocks
Every rock mountain is slowly disintegrating due to erosion, the process being especially rapid above the snow-line. Rock faces are constantly swept by falling stones, which are generally possible to dodge. Falling rocks tend to form furrows in a mountain face, and these furrows (couloirs) have to be ascended with caution, their sides often being safe when the middle is stoneswept. Rocks fall more frequently on some days than on others, according to the recent weather. Ice formed during the night may temporarily bind rocks to the face but warmth of the day or direct sun exposure may easily dislodge these rocks. Local experience is a valuable help on determining typical rockfall on such routes.
The direction of the dip of rock strata often determines the degree of danger on a particular face; the character of the rock must also be considered. Where stones fall frequently debris will be found below, whilst on snow slopes falling stones cut furrows visible from a great distance. In planning an ascent of a new peak mountaineers must look for such traces. When falling stones get mixed in considerable quantity with slushy snow or water a mud avalanche is formed (common in the Himalaya). It is vital to avoid camping in their possible line of fall.
Falling ice
The places where ice may fall can always be determined beforehand. It falls in the broken parts of glaciers (seracs) and from overhanging cornices formed on the crests of narrow ridges. Large icicles are often formed on steep rock faces, and these fall frequently in fine weather following cold and stormy days. They have to be avoided like falling stones. Seracs are slow in formation, and slow in arriving (by glacier motion) at a condition of unstable equilibrium. They generally fall in or just after the hottest part of the day, and their debris seldom goes far. A skillful and experienced ice-man will usually devise a safe route through a most intricate ice-fall, but such places should be avoided in the afternoon of a hot day. Hanging glaciers (i.e. glaciers perched on steep slopes) often discharge themselves over steep rock-faces, the snout breaking off at intervals. They can always be detected by their debris below. Their track should be avoided.
Falls from rocks
The skill of a rock climber is shown by one's choice of handhold and foothold, and his adhesion to those one has chosen. Much depends on a correct estimate of the firmness of the rock where weight is to be thrown upon it. Many loose rocks are quite firm enough to bear a person's weight, but experience is needed to know which can be trusted, and skill is required in transferring the weight to them without jerking. On rotten rocks the rope must be handled with special care, lest it should start loose stones on to the heads of those below. Similar care must be given to handholds and footholds, for the same reason. When a horizontal traverse has to be made across very difficult rocks, a dangerous situation may arise unless at both ends of the traverse there be firm positions. Mutual assistance on hard rocks takes all manner of forms: two, or even three, people climbing on one another's shoulders, or using an ice axe propped up by others for a foothold. The great principle is that of co-operation, all the members of the party climbing with reference to the others, and not as independent units; each when moving must know what the climber in front and the one behind are doing. After bad weather steep rocks are often found covered with a veneer of ice (verglas), which may even render them inaccessible. Crampons are useful on such occasions.
Shelter
Climbers use a few different forms of shelter depending on the situation and conditions. Shelter is a very important aspect of safety for the climber as the weather in the mountains is very unpredictable. Tall mountains require many days of camping on the mountain.
Hut
The European alpine regions, in particular, have a network of mountain huts (called ‘refuges’ in France, ‘cabanes’ in Switzerland and ‘hytte’ in Norway). Such huts exist at many different heights, including in the high mountains themselves – in extremely remote areas bivouac shelters may have been provided. The mountain huts are of varying size and quality but each is typically centred on a communal dining room and have dormitories equipped with mattresses, blankets or duvets, and pillows – guests are expected to bring and to use their own sleeping bag liner. The facilities are usually rudimentary but, given their locations, huts offer vital shelter, make routes more widely accessible (by allowing journeys to be broken and reducing the weight of equipment needing to be carried), and offer good value. In Europe, all huts are staffed during the summer (mid-June to mid-September) and some are staffed in the spring (mid-March to mid-May). Elsewhere, huts may also be open in the fall. Huts also may have a part that is always open, but unmanned, a so-called winter hut. When open and manned, the huts are generally run by full-time employees, but some are staffed on a voluntary basis by members of Alpine clubs (such as Club Alpine Suisse and Club Alpine France). The manager of the hut, termed a guardian or warden in Europe, will usually also sell refreshments and meals – both to those visiting only for the day and to those staying overnight. The offering is surprisingly wide – given that most supplies, often including fresh water, must be flown in by helicopter – and may include glucose-based snacks (such as Mars and Snickers bars) on which climbers and walkers wish to stock up, cakes and pastries made at the hut, a variety of hot and cold drinks (including beer and wine), and high carbohydrate dinners in the evenings. Not all huts do offer a catered service, though, and visitors may need to provide for themselves. Some huts offer facilities for both, enabling visitors wishing to keep costs down to bring their own food and cooking equipment and to cater using the facilities provided. Booking for overnight stays at huts is deemed obligatory, and in many cases is essential as some popular huts – even with over 100 bed spaces - may well be full during good weather and at weekends. Once made, the cancellation of a reservation should be advised to the hut as a matter of courtesy – and, indeed, potentially of safety, as many huts keep a record of where climbers and walkers state they planned to walk to next. Most huts are contactable by telephone and most take credit cards as a means of payment for the service they provide.
Bivy
A bivy or bivouac is simply getting a sleeping bag and Bivouac sack and laying down to sleep. Many times small half sheltered areas like cracks in rocks or simply a trench dug in the snow are used to provide a basic means of shelter as well. This technique is performed by most people only in cases of emergency, however in good weather this can be pleasant. Some climbers steadfastly committed to Alpine Style climbing plan on bivying in order to save the weight of a tent when snow conditions are not suitable for a snow cave.
Tent
Tents are the most common form of shelter used on the mountain. A four season tent is recommended for any camp above timberline in the mountains. Some climbers do not use tents at high altitudes unless the snow conditions do not allow for snow caving. Sometimes walls of snow or rock can be built instead to shelter the tent from high winds and storms. One of the downsides to tenting is that high storm winds and snow loads can be unnerving and cause the tent to collapse. Constant flapping of the tent fabric can hinder sleep and raise doubts about the security of the shelter in windy conditions.
Snow cave
Snow caves are another way for some climbers to shelter high on the mountain. Unlike tents snow caves are silent and actually warmer. A correctly made snow cave will hover around freezing, which relative to outside temperatures can be very warm. They require carrying a snow shovel, which some may consider to be extra equipment, to build easily. They can be dug from a deep snowdrift, out of a slope, or anywhere there is at least four feet of snow. Another shelter that works well is a quinzee, which is excavated from a pile of snow that has been work hardened or sintered (typically by stomping). Igloos are used by some climbers, but are deceptively difficult to build and require specific snow conditions.
Hut
The European alpine regions, in particular, have a network of mountain huts (called ‘refuges’ in France, ‘cabanes’ in Switzerland and ‘hytte’ in Norway). Such huts exist at many different heights, including in the high mountains themselves – in extremely remote areas bivouac shelters may have been provided. The mountain huts are of varying size and quality but each is typically centred on a communal dining room and have dormitories equipped with mattresses, blankets or duvets, and pillows – guests are expected to bring and to use their own sleeping bag liner. The facilities are usually rudimentary but, given their locations, huts offer vital shelter, make routes more widely accessible (by allowing journeys to be broken and reducing the weight of equipment needing to be carried), and offer good value. In Europe, all huts are staffed during the summer (mid-June to mid-September) and some are staffed in the spring (mid-March to mid-May). Elsewhere, huts may also be open in the fall. Huts also may have a part that is always open, but unmanned, a so-called winter hut. When open and manned, the huts are generally run by full-time employees, but some are staffed on a voluntary basis by members of Alpine clubs (such as Club Alpine Suisse and Club Alpine France). The manager of the hut, termed a guardian or warden in Europe, will usually also sell refreshments and meals – both to those visiting only for the day and to those staying overnight. The offering is surprisingly wide – given that most supplies, often including fresh water, must be flown in by helicopter – and may include glucose-based snacks (such as Mars and Snickers bars) on which climbers and walkers wish to stock up, cakes and pastries made at the hut, a variety of hot and cold drinks (including beer and wine), and high carbohydrate dinners in the evenings. Not all huts do offer a catered service, though, and visitors may need to provide for themselves. Some huts offer facilities for both, enabling visitors wishing to keep costs down to bring their own food and cooking equipment and to cater using the facilities provided. Booking for overnight stays at huts is deemed obligatory, and in many cases is essential as some popular huts – even with over 100 bed spaces - may well be full during good weather and at weekends. Once made, the cancellation of a reservation should be advised to the hut as a matter of courtesy – and, indeed, potentially of safety, as many huts keep a record of where climbers and walkers state they planned to walk to next. Most huts are contactable by telephone and most take credit cards as a means of payment for the service they provide.
Bivy
A bivy or bivouac is simply getting a sleeping bag and Bivouac sack and laying down to sleep. Many times small half sheltered areas like cracks in rocks or simply a trench dug in the snow are used to provide a basic means of shelter as well. This technique is performed by most people only in cases of emergency, however in good weather this can be pleasant. Some climbers steadfastly committed to Alpine Style climbing plan on bivying in order to save the weight of a tent when snow conditions are not suitable for a snow cave.
Tent
Tents are the most common form of shelter used on the mountain. A four season tent is recommended for any camp above timberline in the mountains. Some climbers do not use tents at high altitudes unless the snow conditions do not allow for snow caving. Sometimes walls of snow or rock can be built instead to shelter the tent from high winds and storms. One of the downsides to tenting is that high storm winds and snow loads can be unnerving and cause the tent to collapse. Constant flapping of the tent fabric can hinder sleep and raise doubts about the security of the shelter in windy conditions.
Snow cave
Snow caves are another way for some climbers to shelter high on the mountain. Unlike tents snow caves are silent and actually warmer. A correctly made snow cave will hover around freezing, which relative to outside temperatures can be very warm. They require carrying a snow shovel, which some may consider to be extra equipment, to build easily. They can be dug from a deep snowdrift, out of a slope, or anywhere there is at least four feet of snow. Another shelter that works well is a quinzee, which is excavated from a pile of snow that has been work hardened or sintered (typically by stomping). Igloos are used by some climbers, but are deceptively difficult to build and require specific snow conditions.
Technique on Mountaineering
Snow
While certain compacted snow conditions allow mountaineers to progress on foot, typically some form of mechanical device is required to travel efficiently over snow & ice. Crampons are device having 10-12 spikes which are attached to a mountaineers boots, are used on hard snow (neve) and ice to provide additional traction & allow very steep ascents and descents. There are many different varieties, ranging from lightweight aluminum models intended for walking on glaciers to aggressive steel models intended for vertical and overhanging ice and rock. Snowshoes can be used to walk through deep snow approaching the mountain or on lesser slopes up the mountain. Skis can be used almost everywhere snowshoes can and also in steeper, more alpine landscapes although it takes more practice to develop sufficiently strong skiing skills for difficult terrain. The practice of combining the techniques of alpine skiing and mountaineering to ascend and descend a mountain is a form of the sport by itself, called Ski Mountaineering. Ascending and descending a snow slope involves many different techniques of the feet and an ice axe which have been developed over the last hundred years, originating in Europe. The progression of footwork from the lowest angle slopes to the steepest terrain is first to splay the feet to a rising traverse, to kick stepping, to front pointing the crampons. The progression of the ice axe technique from the lowest angle slopes to the steepest terrain is to use the ice axe first as a walking stick, then a stake, then to use the front pick as a dagger below the shoulders or above, and finally to swing the pick into the slope over the head. This also involves different designs of ice axe depending on the terrain to be covered, and even whether a mountaineer uses one or two ice axes.
Glaciers
When traveling over glaciers, crevasses pose a grave danger. These giant cracks in the ice are not always visible as snow can be blown and freeze over the top to make a snowbridge. At times snowbridges can be as thin as a few inches. Climbers use a system of ropes to protect themselves from such hazards. Basic gear for glacier travel includes crampons and ice axes. Teams of two to five climbers tie into a rope equally spaced. If a climber begins to fall the other members of the team perform a self-arrest to stop the fall. The other members of the team enact a crevasse rescue to pull the fallen climber from the crevasse.
Ice
Multiple methods are used to safely travel over ice. If the terrain is steep but not vertical, then protection in the form of pickets or ice screws can be driven into the snow or ice and attached to the rope by the lead climber. Each climber on the team must clip past the anchor, and the last climber picks up the picket. This allows for safety should the entire team be taken off their feet. This technique is known as Simul-climbing.
If the terrain becomes vertical then standard ice climbing techniques are used.
While certain compacted snow conditions allow mountaineers to progress on foot, typically some form of mechanical device is required to travel efficiently over snow & ice. Crampons are device having 10-12 spikes which are attached to a mountaineers boots, are used on hard snow (neve) and ice to provide additional traction & allow very steep ascents and descents. There are many different varieties, ranging from lightweight aluminum models intended for walking on glaciers to aggressive steel models intended for vertical and overhanging ice and rock. Snowshoes can be used to walk through deep snow approaching the mountain or on lesser slopes up the mountain. Skis can be used almost everywhere snowshoes can and also in steeper, more alpine landscapes although it takes more practice to develop sufficiently strong skiing skills for difficult terrain. The practice of combining the techniques of alpine skiing and mountaineering to ascend and descend a mountain is a form of the sport by itself, called Ski Mountaineering. Ascending and descending a snow slope involves many different techniques of the feet and an ice axe which have been developed over the last hundred years, originating in Europe. The progression of footwork from the lowest angle slopes to the steepest terrain is first to splay the feet to a rising traverse, to kick stepping, to front pointing the crampons. The progression of the ice axe technique from the lowest angle slopes to the steepest terrain is to use the ice axe first as a walking stick, then a stake, then to use the front pick as a dagger below the shoulders or above, and finally to swing the pick into the slope over the head. This also involves different designs of ice axe depending on the terrain to be covered, and even whether a mountaineer uses one or two ice axes.
Glaciers
When traveling over glaciers, crevasses pose a grave danger. These giant cracks in the ice are not always visible as snow can be blown and freeze over the top to make a snowbridge. At times snowbridges can be as thin as a few inches. Climbers use a system of ropes to protect themselves from such hazards. Basic gear for glacier travel includes crampons and ice axes. Teams of two to five climbers tie into a rope equally spaced. If a climber begins to fall the other members of the team perform a self-arrest to stop the fall. The other members of the team enact a crevasse rescue to pull the fallen climber from the crevasse.
Ice
Multiple methods are used to safely travel over ice. If the terrain is steep but not vertical, then protection in the form of pickets or ice screws can be driven into the snow or ice and attached to the rope by the lead climber. Each climber on the team must clip past the anchor, and the last climber picks up the picket. This allows for safety should the entire team be taken off their feet. This technique is known as Simul-climbing.
If the terrain becomes vertical then standard ice climbing techniques are used.
Mountaineering
Mountaineering is the sport, hobby or profession of walking, hiking, trekking and climbing up mountains. It is also sometimes known as alpinism, particularly in Europe. While it began as an all-out attempt to reach the highest point of unclimbed mountains, it has branched into specializations addressing different aspects of mountains and may now be said to consist of three aspects: rock-craft, snow-craft and skiing, depending on whether the route chosen is over rock, snow or ice. All require great athletic and technical ability, and experience is also a very important part of the matter.
Selasa, 15 Januari 2008
Geology of Grand Canyon
The principal consensus among geologists is that the Colorado River basin (of which the Grand Canyon is a part) has developed in the past 40 million years and that the Grand Canyon itself is probably less than five to six million years old (with most of the downcutting occurring in the last two million years). The result of all this erosion is one of the most complete geologic columns on the planet.
Looking down Bright Angel trail to the Grand Canyon. The green area is Indian Gardens and the trail continues to Phantom Ranch at the river where a suspension bridge allows access to the North Rim.
Looking down Bright Angel trail to the Grand Canyon. The green area is Indian Gardens and the trail continues to Phantom Ranch at the river where a suspension bridge allows access to the North Rim.
The major geologic exposures in Grand Canyon range in age from the 2 billion year old Vishnu Schist at the bottom of the Inner Gorge to the 230 million year old Kaibab Limestone on the Rim. Interestingly, there is a gap of about one billion years between the stratum that is about 500 million years old and the lower level, which is about 1.5 billion years old. That indicates a period of erosion between two periods of deposition.
Many of the formations were deposited in warm shallow seas, near-shore environments (such as beaches), and swamps as the seashore repeatedly advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which most geologists claim was laid down as sand dunes in a desert, and several parts of the Supai Group.
The great depth of the Grand Canyon and especially the height of its strata (most of which formed below sea level) can be attributed to 5,000 to 10,000 feet (1500 to 3000 m) of uplift of the Colorado Plateau, starting about 65 million years ago (during the Laramide Orogeny). This uplift has steepened the stream gradient of the Colorado River and its tributaries, which in turn has increased their speed and thus their ability to cut through rock (see the elevation summary of the Colorado River for present conditions).
Weather conditions during the ice ages also increased the amount of water in the Colorado River drainage system. The ancestral Colorado River responded by cutting its channel faster and deeper.
The base level and course of the Colorado River (or its ancestral equivalent) changed 5.3 million years ago when the Gulf of California opened and lowered the river's base level (its lowest point). This increased the rate of erosion and cut nearly all of the Grand Canyon's current depth by 1.2 million years ago. The terraced walls of the canyon were created by differential erosion.
About one million years ago, volcanic activity (mostly near the western canyon area) deposited ash and lava over the area, which at times completely obstructed the river. These volcanic rocks are the youngest in the canyon.
Looking down Bright Angel trail to the Grand Canyon. The green area is Indian Gardens and the trail continues to Phantom Ranch at the river where a suspension bridge allows access to the North Rim.
Looking down Bright Angel trail to the Grand Canyon. The green area is Indian Gardens and the trail continues to Phantom Ranch at the river where a suspension bridge allows access to the North Rim.
The major geologic exposures in Grand Canyon range in age from the 2 billion year old Vishnu Schist at the bottom of the Inner Gorge to the 230 million year old Kaibab Limestone on the Rim. Interestingly, there is a gap of about one billion years between the stratum that is about 500 million years old and the lower level, which is about 1.5 billion years old. That indicates a period of erosion between two periods of deposition.
Many of the formations were deposited in warm shallow seas, near-shore environments (such as beaches), and swamps as the seashore repeatedly advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which most geologists claim was laid down as sand dunes in a desert, and several parts of the Supai Group.
The great depth of the Grand Canyon and especially the height of its strata (most of which formed below sea level) can be attributed to 5,000 to 10,000 feet (1500 to 3000 m) of uplift of the Colorado Plateau, starting about 65 million years ago (during the Laramide Orogeny). This uplift has steepened the stream gradient of the Colorado River and its tributaries, which in turn has increased their speed and thus their ability to cut through rock (see the elevation summary of the Colorado River for present conditions).
Weather conditions during the ice ages also increased the amount of water in the Colorado River drainage system. The ancestral Colorado River responded by cutting its channel faster and deeper.
The base level and course of the Colorado River (or its ancestral equivalent) changed 5.3 million years ago when the Gulf of California opened and lowered the river's base level (its lowest point). This increased the rate of erosion and cut nearly all of the Grand Canyon's current depth by 1.2 million years ago. The terraced walls of the canyon were created by differential erosion.
About one million years ago, volcanic activity (mostly near the western canyon area) deposited ash and lava over the area, which at times completely obstructed the river. These volcanic rocks are the youngest in the canyon.
Senin, 14 Januari 2008
Geography of Grand canyon
The Grand Canyon is a massive rift in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata and is also one of the six distinct physiographic sections of the Colorado Plateau province. The Grand Canyon is unmatched throughout the world for the vistas it offers to visitors on the rim. It is not the deepest canyon in the world — both the Cotahuasi Canyon (11598 feet or 3535 m), Colca Canyon (10499 feet or 3200 m), both in Arequipa, Peru and Hell's Canyon on the Oregon-Idaho border are deeper — but Grand Canyon is known for its overwhelming size and its intricate and colorful landscape. Geologically it is significant because of the thick sequence of ancient rocks that are beautifully preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent.
Uplift associated with mountain building events later moved these sediments thousands of feet upward and created the Colorado Plateau. The higher elevation has also resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid. The uplift of the Colorado Plateau is uneven, and the north-south trending Kaibab Plateau that Grand Canyon bisects is over a thousand feet higher at the North Rim (about 1,000 ft/300 m) than at the South Rim. The fact that the Colorado River flows in a curve around the higher North Rim part of the Kaibab Plateau and closer to the South Rim part of the plateau is also explained by this asymmetry. Ivo Lucchitta of the U.S. Geological Survey first suggested that, as the Colorado River developed before significant erosion of the region, it naturally found its way across or around the Kaibab Uplift by following a "racetrack" path to the south of the highest part of the plateau. Almost all runoff from the North Rim (which also gets more rain and snow) flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon (following the general tilt). The result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side.
Temperatures on the North Rim are generally lower than the South Rim because of the greater elevation (averaging 8,000 ft/2,438 m above sea level).[2] Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon (Arizona State Route 67) is limited during the winter season due to road closures. Views from the North Rim tend to give a better impression of the expanse of the canyon than those from the South Rim.
Uplift associated with mountain building events later moved these sediments thousands of feet upward and created the Colorado Plateau. The higher elevation has also resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid. The uplift of the Colorado Plateau is uneven, and the north-south trending Kaibab Plateau that Grand Canyon bisects is over a thousand feet higher at the North Rim (about 1,000 ft/300 m) than at the South Rim. The fact that the Colorado River flows in a curve around the higher North Rim part of the Kaibab Plateau and closer to the South Rim part of the plateau is also explained by this asymmetry. Ivo Lucchitta of the U.S. Geological Survey first suggested that, as the Colorado River developed before significant erosion of the region, it naturally found its way across or around the Kaibab Uplift by following a "racetrack" path to the south of the highest part of the plateau. Almost all runoff from the North Rim (which also gets more rain and snow) flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon (following the general tilt). The result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side.
Temperatures on the North Rim are generally lower than the South Rim because of the greater elevation (averaging 8,000 ft/2,438 m above sea level).[2] Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon (Arizona State Route 67) is limited during the winter season due to road closures. Views from the North Rim tend to give a better impression of the expanse of the canyon than those from the South Rim.
The Grand Canyon
The Grand Canyon is a colorful steep-sided gorge carved by the Colorado River in the U.S. state of Arizona. It is largely contained within the Grand Canyon National Park — one of the first national parks in the United States. President Theodore Roosevelt was a major proponent of preservation of the Grand Canyon area, and visited on numerous occasions to hunt and enjoy the scenery.
The canyon, created by the Colorado River over a period of 6 million years, is 277 miles (446 km) long, ranges in width from 4 to 18 miles (6.4 to 29 km) and attains a depth of more than a mile (1.6 km). Nearly two billion years of the Earth's history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted.
During prehistory, the area was inhabited by Native Americans who built settlements within the canyon and its many caves. The Pueblo people considered the Grand Canyon ("Ongtupqa" in Hopi language) a holy site and made pilgrimages to it.
The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540.
The Grand Canyon was largely unexplored until after the U.S. Civil War. In 1869, Major John Wesley Powell, a one-armed Civil War veteran with a thirst for science and adventure, made the first recorded journey through the canyon on the Colorado River. He accomplished this trek with nine men in four small wooden boats, though only six men completed the journey. Powell referred to the sedimentary rock units exposed in the canyon as "leaves in a great story book".
The canyon, created by the Colorado River over a period of 6 million years, is 277 miles (446 km) long, ranges in width from 4 to 18 miles (6.4 to 29 km) and attains a depth of more than a mile (1.6 km). Nearly two billion years of the Earth's history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted.
During prehistory, the area was inhabited by Native Americans who built settlements within the canyon and its many caves. The Pueblo people considered the Grand Canyon ("Ongtupqa" in Hopi language) a holy site and made pilgrimages to it.
The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540.
The Grand Canyon was largely unexplored until after the U.S. Civil War. In 1869, Major John Wesley Powell, a one-armed Civil War veteran with a thirst for science and adventure, made the first recorded journey through the canyon on the Colorado River. He accomplished this trek with nine men in four small wooden boats, though only six men completed the journey. Powell referred to the sedimentary rock units exposed in the canyon as "leaves in a great story book".
Langganan:
Postingan (Atom)
