This is one of 130 craters in the 25 kilometer long, Lakagígar, volcanic fissure. The eruption that created these craters occurred in the year 1783 and went on for 8 months. This is possibly the hardest time in Icelandic history. Crops failed, most livestock perished and temperatures dropped as an ash filled haze blocked the sun for years. A quarter of the Icelandic population died as a result of the famine that ensued.
The lava flow is the greatest in historical times in the world. Up to 6.000 cubic meters of molten lava flowed every second from the craters. To put this in some sort of scale, the largest river in Iceland has an average flow of 400 cubic meters per second. In total the volcanic material was around 15 km3, covering 600 km2 or 0.5% of Iceland. The lava fountains are likely to have reached up to 1.4 km up into the sky and the ash cloud will have climbed as high as 15 km. Contemporary accounts describe it as a red chandelier far up in the mountains.
The effect of such an eruption is not limited to Iceland. Just as in the more recent Eyjafjallajökull eruption, ash was carried around the world. However this was many times greater than the recent eruption and caused much more harm than cancelled flights. The poisonous gases and ash killed tens of thousands in mainland Europe. It is estimated that around 50.000 died in Britain as a result of the gases and famine.
The ash in atmosphere caused freak weather around the world in the next few years. Heat waves in Europe, the Mississippi River frozen at New Orleans, Ice in the Gulf of Mexico and droughts in Japan. One sixth of Egyptians are thought to have died in a famine caused by low water levels in the Nile attributed to the ash. Famine and crop fluctuations in France as a result of the eruption are contributing factors to the anger and troubles that led to the French Revolution.
It is not a question if, but when, another eruption of this scale occurs. Hopefully we will not live to experience such a disaster in our lifetimes. Iceland is entirely built upon lava from eruptions such as these, so this was not a unique event.