Lightning and hiking safety

LIGHTNING and HIKING and CAMPING

Lightning is one of nature’s wonderful sights. However those that go camping, backpacking and hiking and those that play golf are all too aware of the many accidents and unfortunate fatalities that occur when caught out in the open.

Strikes cause along with death and injury an enormous amount of damage, in particular in the telecommunications and electrical power distribution industries.

More than a 1000 people are killed worldwide annually by strikes, and in the USA lightning transient damage exceeds 1 billion dollars.

It is a fact that there are some 100 lightning strikes in the world every second. Prediction of lightning strikes is hard and you cant prevent a lightning strike.

If you intend hiking or camping in an area where there is higher activity then it is very sensible to be aware of the risks and take adequate precautions.

HOW FAR AWAY IS THE STORM?

The traditional maxim for determining how far away the activity is generally revolves around counting the number of seconds between the observed flash and the resulting thunder. 5 seconds is equivalent to approximately 1 mile.

The general advice is that if it is closer than 7 miles or 35 seconds then you should be taken safety precautions. It is a fact that lightning strikes can jump 7 miles between strikes, it is a myth that it is a gradual process.

TAKING COVER FROM LIGHTNING

1. Avoid open spaces or high ground, and do not shelter under tall trees or small stand soft trees. Standing under a lone tree that gets struck is dangerous, either the electricity traveling down the tree radiates into the ground around you, but also the bark and wood often explodes and many have been injured by this material. If you can shelter in a building or a vehicle you should do so. You should avoid all metal objects that include overhead electric cables, wire fences and also portable rain and sun shelters, this includes tents with metal tent poles.

2. Do not stand near electricity towers made from steel as a strike traveling down the tower will radiate out into ground around where you are standing

3. Do not shelter near small lakes and dams full of water, water is conductive

4. Look for gullies, large caves in the rock formations, seek refuge in the low ground.

5. Crouch down or even lie down, keep feet together and make yourself into a low profile target. Make sure the group spreads out with at least 15 feet between each person. Also cover your ears as a strike thunderclap can be deafening. Don’t restart hiking activities or open area activities for at least 30 minutes after storm appears to have passed

6. If someone within your hiking or camping group is struck by lightning and is not breathing start CPR immediately, you have a good chance of them recovering, but do not delay this at all, above all don’t panic. Most survive the ordeal and you are quite safe to touch them. Call emergency services and get the person to medical help as soon as possible

What Causes Lightning – Lightning 101 - The Physics

What causes lightning? A quick refresher course called lightning 101 is in order. Within the cloud formation, strong updrafts and downdrafts generate high electrical charges. When the voltage reaches a sufficiently high level both cloud to cloud and ground discharges occur. Strikes occur when the ground is at positive polarity and the cloud negative region attempts to equalise with ground. Alternatively strikes can occur when the positively charged cloud top equalises with the negative ground, or when the positive charged ground equalises with the negative charge cloud or the negatively charged ground equalises with the positive charged cloud top.

Lightning consists of a number of components which form a multidirectional flow of charges. Peak currents can exceed 200,000 amperes (200kA) at over 30,000°C for a matter of milliseconds (25-100 mS). The positively charged ions rise to the cloud top, and the negative ions migrate to the cloud base. Regions of positive charged ions also form at the cloud base. Eventually the cloud charge levels have sufficient potential difference between ground or another cloud to discharge. The processes are as follows:

Leader The leader consists is a negative stream of electrons consisting of many small forks or fingers that follow and break down the air paths offering the least resistance. The charge follows the fork finding the easiest path as each successive layer is broken down and charged to the same polarity as the cloud charge.

Upward Positive Leader This is a positive charge that rises some 50 metres above the ground.

Channel When the two meet a channel is formed.

Return Stroke This path is generally much brighter and more powerful than the leader, and travels upwards to the cloud partially equalising the potential difference between ground and cloud.

Dart Leader In a matter of milliseconds after the return stroke, another downwards charge takes place following the same path as the stepped leader and return stroke, sometimes followed by multiple return strokes (multipulse surges).

Multipulse Surges These occur in over 70% of strikes. This phenomenon is where up to 20 restrikes follow the initial strike at intervals of around 10-200 milliseconds apart. In addition continuing currents of 200-500 amps with durations of up to 1-2 seconds may also occur. The movements happen so fast that it appears to be a single event. This sequence can continue until the differential between cloud and ground has been equalised.