[4] The outer caldera of Askja, representing a prehistoric eruption, is about 50 km2 (19 sq mi) in area, and there is evidence of other later caldera-forming events within it.

Being situated in the rain shadow to the northeast of the Vatnajökull glacier, the area receives only about 450 mm (18 in) of rainfall annually.

Ash more than 1 cm in thickness covered 5,000 km2 (1,900 sq mi) and the total population in Iceland of sheep declined by 2% and cattle by 6.2% between 1874 and 1876.

[9] Another less well-known large rhyolitic eruption, called Askja-S (Skolli), occurred in the early Holocene, 10,824 ± 97 years BP.

In early April 2012 it was noted that the lake in the caldera was totally clear of ice, which usually does not happen until in June or July in a normal year.

[14] In early September 2021, GPS and Satellite data showed that an inflation at the rate of five cm per month, most likely attributed to magma intrusion, of the caldera had started in August.

[15] An Article published on September 9 from the Icelandic Meteorological Office(IMO) stated the Aviation Color Code was upgraded from "Green" to "Yellow" due to the changes.

[16] The Article also says, "Next week IMO and the Institute of Earth Sciences (UÍ) will potentiate the monitoring network around Askja to allow a better coverage and surveillance of the volcano."

[17] In 1907, the German scientists Walter von Knebel and Max Rudloff visited Askja to study the caldera.

Following local publicity of the plight of farming communities in May 1775, and a letter to The Times in July 1775, fund-raising efforts in the UK, Denmark, and Norway took place and relief supplies were organised.

A deposit paid to the Danish Governor of Iceland and advertising emphasising the impact of the eruption eased the Canadian plan.

There are two mountain huts and a campsite at Dreki [ˈtrɛːcɪ], by Drekagil, which is about 100 km (62 mi) by a 4x4 F-road, from the Icelandic ring-road.