Lightning Poses Some Interesting and Unique Problems for Summer Mountaineering
Generally speaking lightning activity increases with altitude. Being below the tree line in dense forests can make it difficult to see the sky and watch approaching clouds. Above the tree line and at higher elevations, thunder rolling through canyons and valleys can make it next to impossible to know what direction the storm is coming from and in some cases if it is even in your immediate area. Finally, storm clouds can suddenly form or pass over the top of a ridge making things nasty for the “mountain topper” in a matter of minutes.
Signs of an impending thunderstorm can be high thin clouds streaking overhead, dark rising columns of “cotton balls” with shredded tops or dark bases with jagged torn bottoms. When you start to hear thunder it is time to be alert.
Knowing the right things to do during a thunderstorm can help keep your group safe and alive. One of the most common questions people ponder is what are the odds of being hit by lightning. Although some sources have tried to put a statistical number to it, like 1 in 3,000,000, it isn’t that simple. Your odds of being hit by lighting vary by the activity you engage in, when you engage in outdoor activity, and where you spend most of your time outdoors.
Physics of Lightning
Lightning arises from a separation of electrical charges, either between clouds, or between cloud and earth. This separation of charge occurs when there are strong vertical updrafts of air acting on raindrops, resulting in tremendous electrical potential differences.
The strong upward air currents may occur due to unequal solar heating of neighbouring areas, such as over freshly plowed fields and lakes. This thermal mechanism causes updrafts and resulting thunderheads and electrical activity over plains and other nonmountainous areas, but may also act in the mountains, in differential heating of air over valley floors and mountain ridges due to different ground cover. Lightning storms of this thermal origin will normally occur during the afternoon.
Another mechanism creating vertical updrafts of particular interest to mountaineers is the very presence of the mountain slopes forcing otherwise horizontally moving air to flow upwards. A major change of weather such as a front moving through can cause a thunderstorm at any time of day. With appropriate moisture content in the air, electrical charge separation and consequent potential differences will result.
Strong and obvious vertical development of clouds indicates a high probability of lightning. Normally air is a good insulator, but in the presence of sufficiently large potential gradients, it will ionize, or break down, and conduct electrical currents quite well. The lightning flash is, crudely speaking, the flow of the separated electrical charges back together, again along ionized air. Since potential gradients are largest near high and relatively sharp points, breakdown of the air and lightning will most likely occur in such locations.
The two most important dangers from lightning are the direct hit and the ground currents. The first of these, as mentioned above, is most likely to occur at a sharply pointed feature such as a mountain summit, a sharp ridge or minor summit pinnacle at the end of a ridge. A tree or a standing person is another likely target. Furthermore, a relatively small object such as a person is less likely to be hit when in a large concave terrain feature such as a bowl than on a convex surface such as a knoll or large bench. The current that flows in the lightning bolt does not dissipate itself at the point of direct hit, but tends to flow along the easiest paths of electrical conduction on the surface of the ground. These ground currents will be strongest near the point of direct hit, rapidly diminishing in intensity with distance; but even well away from the direct hit, the ground currents can be deadly.
Ground Currents. To avoid injury from ground currents, the climber should first of all stay out of the easy paths of current. Such easy paths include anything wet, and particularly wet lichen-covered rocks, cracks and crevasses filled with water, and wet earth. Other easy paths include wet ropes, cables, etc., along the ground. Also, short straight path through the air may be easy compared to longer paths along the ground itself.
The body is an easy path, and thus a climber should not get in the situation shown in Fig. 2 (below), or in a similar one, sitting in a depression in the ground across which currents might jump through the person. Avoid contact with the ground, squat on your pack, rope or ensulite. Electrical currents are forced through the body by potential differences that are developed along the path of the ground currents. Thus, to minimize current through the body, one’s feet should be kept close together, and the climber should be facing along, rather than across the most likely direction of current flow. His hands should be kept off the ground to prevent current from flowing directly through the vital organs as discussed below. The person sitting as in Fig.2 is more susceptible to injury than if he was squatting on his feet alone.
Ground currents will be quite small along a dry path and thus it appears that a safe place might be under an overhang or in a cave. The danger of being at the mouth of a cave, as in Fig.1, was mentioned above – a direct spark might occur across the cave opening and pass through the body. There is also danger in being near an interior cave wall, because it is quite possible that an easy path for current exists through the ground to the cave interior, for example along a drainage crevasse. It is then possible for a discharge to occur from the entrance of this crevasse into the cave through a person to the cave. A small cave may give a false sense of security. The best measure to take against being injured by lightning in the mountains is to be off the mountain; thus a speedy descent during an impending lightning storm is appropriate.
Such descent is likely to involve rappelling, which may be exceedingly dangerous in electrical activity and rain because a wet rope is a very easy path for current. The potential difference between the rappeller and the rock at his feet may be essentially the potential developed along the ground over the distance from the rappel anchor to the rappeller, and a large current may be easily passed along the ropes trough the body. Even a minor shock may be indirectly fatal, if it causes the rappeller to fall out of his rappel. Thus rappelling involves a calculated risk. It speeds descent and escape from a danger area, but greatly increases hazard in the process.
A climber in a location exposed in the climber sense of the word but moderately safe from severe lightning hazards could experience a minor shock that would cause him to fall. Thus he should be tied to a secure anchor. Since his tie-in rope to the anchor will be a conductor to some extent, the rope should lie across rather than along possible paths of ground current to prevent a large potential from developing between the anchor point and the position of the climber. The rope should certainly not go to a chest sling, which would cause any current to flow through the heart and spinal cord (See physiology section).
Any measures taken to prevent injury from lightning will involve minimization of potential differences from one part of the body to an other. Thus the best body position is the crouch, in a location as in Fig.1. The feet should be kept close together, and preferably on a small dry rock or other insulator such as a pack or a rope, and the hands kept off the ground (Important). A metal pack frame may be used to great advantage by laying it on the ground and squatting on it – Any currents would tend to pass through the metal rather than the body.
An ice-axe certainly should not be worn on a pack pointing up, but there is no reason to throw away the axe or other small metal object including climbing hardware, since these items may be needed later and they do not attract lightning when in the pack or on the body. A lightning discharge is more likely to occur from the body itself than from a small object worn on the person.
Protection from direct hit. We now consider protection from direct hit. Obviously the best solution is to be completely off the mountain. Assuming that this is possible, advantage can be taken of the presence of a nearby prominent pinnacle or other likely spot of direct stroke. Lightning will tend to hit the pinnacle rather than a person near the pinnacle if the pinnacle is five to ten times or more the person’s height and if the horizontal distance from the person to the peak is about half the pinnacle height. If the potential victim gets too close under the peak, his body may be an alternate path to that of the ground for the very strong ground currents.
If he gets into a cave, as in Fig. 2, he may be sitting in a spark gap and thus be exposed for a minor direct hit if the currents prefer to take the direct path through the air across the mouth of the cave rather than the longer path along the ground. Also, if the person moves far from under the pinnacle, (more than its height), the direct hit might just as likely strike the victim as the pinnacle. A climber might find relative safety just down below a sharp ridge as well as near a peak or a pinnacle or a gendarme. The theory behind a lightning rod on a roof is related to the above, that is, it is hoped that the lightning may strike the rod rather than the roof, and the currents would then be conducted safely to ground. Furthermore, a sharp projection many serve to discharge gradually the charge – holding cloud over it without a lightning bolt perpetually striking, but the mountaineer should never count on this.
Physiology Electrical currents through the body may cause not only burns but also involuntary muscle contraction, stoppage of the heart, improper functioning of the brain and other consequent malfunctioning of the body such as cessation of breathing. A person is not electrified after being hit by lightning and a full 80% of people that are hit by lightning recover.
The extent of the damage depends on the amplitude and duration of the current sent on the path of the flow through the body. When a person is struck directly, the currents are likely to be so large that no matter what the path through the body may be, the results are fatal. But ground currents are much weaker, and the particular current path through the body makes a significant difference. It is also possible for someone to be hit by lightning and be practically uninjured. For example, current from hand to hand will pass through the heart, spinal cord and vital organs and may be fatal; but the same current from foot to knee of the same leg is not so bad.
First aid may include heart massage, artificial respiration, and treatment for traumatic shock, hypothermia and burns. If a member of your party gets hit by lightning start emergency treatment immediately. If a person has no pulse or heartbeat start performing CPR. Treat electrical burns as you would any other. Neurological and internal injuries are possible. Mountaineers should be familiar with such treatments and be prepared to administer them.
In the mountains you can greatly prevent your odds of being hit by lightning:
Get out of open and exposed areas. Ridges and open fields leave you exposed. Sharp changes in terrain like the edge of water, the edges of a forest, rocks to dirt, etc. are naturally more hazardous.
Nearby tall objects like solitary trees, communication antenna, or rock spires (tallest object around) serve as natural lightning rods. Find an area with trees of uniform height or an area with low brush and bushes. Never seek shelter directly under a tree. If you cannot find any shelter at all, say when you are above the tree line, get as low as possible.
If in a region of high lightning danger, individuals should not wait out the storm huddled together. Spread out at least 20 feet as lightning can jump this far and injure everyone in a tight group. The survival of one person whose heart or breathing has been stopped by a stroke of lightning will depend critically on prompt action by companions, and it is quite unlikely that all of a group of separated persons will be knocked unconscious simultaneously.
If you have metal gear like carabineers, picks, or crampons remove them and set your gear away from you. Sit on top of your pack if you have one with your feet on the ground, crouched down with your eyes closed and your hands over your ears. Sight and hearing injuries are very common among lightning strike victims and near strike injuries. Do not lie prone on the ground; this is no longer recommended as a safe position.
Lightning can originate from six to eight miles away from its last origin, so it is possible for a “bolt from the blue” on the edge of a storm. This is why if you wait until you see lightning, it may be already too late to take action. If your hair stands on end, you feel a tingling sensation, or if the area around you appears electrified, lightning may be ready to strike. Make yourself the smallest possible target and attempt to minimize your contact with the ground, Hold your breath, some people have been seriously injured when they breathe in the superheated air that surrounds and is expanding out from a lightning bolt.
Wait for at least 30 minutes after the lightning and thunder has stopped to move on and resume activity.