Rauðibotn is part of the Eldgjá craters, a chain of volcanic craters which stretches through the Central Highlands from Mýrdalsjökull glacier to Vatnajökull glacier. Eldgjá is connected to the monster Katla (volcano), as both are part of the same volcanic system. Eldgjá has only erupted once since the VIking settlement of Iceland in the 9th century: In 934 a massive eruption, believed to be the largest volcanic eruption to take place in Iceland in the past millennia.
The 934 eruption produced a lava field which covers approximately 800 square kilometers (310 square miles), 18 cubic kilometers (4.3 cubic miles) of lava and 5-7 cubic kilometers (1.2-1.7 cubic miles) of tephra and ash. The size of the lava field is large enough to cover all of New York City, and then some.
The impact of the eruption on global weather systems was catastrophic, causing crop failures and hunger in Europe. Temperatures all over the Northern Hemisphere dropped, causing rivers as far as present day Iran to have frozen over.