Lightning is an atmospheric electrostatic discharge (spark) accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms. From this discharge of atmospheric electricity, a leader of a bolt of lightning can travel at speeds of 220,000 km/h (140,000 mph), and can reach temperatures approaching 30,000 °C (54,000 °F), hot enough to fuse silica sand into glass channels known as fulgurites which are normally hollow and can extend some distance into the ground. There are some 16 million lightning storms in the world every year.Lightning causes ionisation in the air through which it travels, leading to the formation of nitric oxide and ultimately, nitric acid, of benefit to plant life below.
Lightning can also occur within the ash clouds from volcanic eruptions, or can be caused by violent forest fires which generate sufficient dust to create a static charge. continue..

Lightning Can Strike Twice. Cloud-to-ground lightning bolts are a common phenomenon—about 100 strike Earth’s surface every single second—yet their power is extraordinary. Each bolt can contain up to one billion volts of electricity.
This enormous electrical discharge is caused by an imbalance between positive and negative charges. During a storm, colliding particles of rain, ice, or snow increase this imbalance and often negatively charge the lower reaches of storm clouds. Objects on the ground, like steeples, trees, and the Earth itself, become positively charged—creating an imbalance that nature seeks to remedy by passing current between the two charges.
A step-like series of negative charges, called a stepped leader, works its way incrementally downward from the bottom of a storm cloud toward the Earth. Each of these segments is about 150 feet (46 meters) long. When the lowermost step comes within 150 feet (46 meters) of a positively charged object it is met by a climbing surge of positive electricity, called a streamer, which can rise up through a building, a tree, or even a person. The process forms a channel through which electricity is transferred as lightning. continue..

Lightning is caused by the build up of electrostatic charge in clouds.   One region within the cloud builds up a positive charge and the other a negative charge.  The process is not completely understood as to why, but the bottom of the cloud usually ends up being negatively charged and the top positively charged.  If the build up (separation) of charge becomes great enough, the negative charges may leap to the positive side of another cloud, this is called sheet lightning or it may leap to the ground.  The animation shows he creation of a ground strike of lightning. continue..

Lightning is the most spectacular element of a thunderstorm. In fact it is how thunderstorms got their name. Wait a minute, what does thunder have to do with lightning? Well, lightning causes thunder. Lightning is a giant spark. A single stroke of lightning can heat the air around it to 30,000 degrees Celsius (54,000 degrees Fahrenheit)! This extreme heating causes the air to expand at an explosive rate. The expansion creates a shock wave that turns into a booming sound wave, better known as thunder. This explains why it has the name thunderstorm. Thunder and lightning occur at roughly the same time, although you see the flash of lightning before you hear the thunder. This is because light travels much faster than sound. continue..

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