The effluent river Laxá [ˈlaksˌauː] is known for its rich fishing for brown trout and Atlantic salmon.

The lake is fed by nutrient-rich springwater and has a high abundance of aquatic insects (Chironomidae) and Cladocera that form an attractive food supply for ducks.

The population of the Barrow's goldeneye (of about 2000 individuals) relies entirely on the habitat provided by the Mývatn Laxá water system and its surrounding lava fields.

Most of the Barrow's goldeneyes overwinter there, using ice-free areas kept open by emerging spring water (both warm and cold) and in the strong river current.

This species is a hole-nester, in North America using tree-holes, but at Mývatn the birds use cavities in the lava for nesting.

To ensure sustainability, the harvesting follows strict age-old rules of leaving at least four eggs in a nest for the duck to incubate.

The lava flows and moorlands surrounding the lake are home to rock ptarmigans and occasionally gyr falcons may be present.

Due to environmental factors their population has rapidly declined and the algae appeared to have become extinct in 2013.

The lava flowed down the valley Laxárdalur to the lowland plain of Aðaldalur [ˈaːðalˌtaːlʏr̥] where it entered the Arctic Ocean about 50 km away from Mývatn.

The crater row that formed along the eruptive fissure is called Þrengslaborgir [ˈθreiŋstlaˌpɔrcɪr̥] (or Lúdentarborgir [ˈluːˌtɛn̥tarˌpɔrcɪr̥]) and has often been used as a textbook example of this type of volcanic activity.

A group of such craters at Skútustaðir [ˈskuːtʏˌstaːðɪr̥] on the south shore of the lake is protected as a natural monument.

The Mývatn district lies on the western border of the volcanic zone which cuts across north-eastern Iceland from north to south and is an extension of the Mid-Atlantic Ridge.

About 3800 years ago the shield volcano Ketildyngja [ˈcʰɛːtɪlˌtiɲca] was formed about 25 km south-east of Mývatn, and from it a huge lava flow, the Older Laxá-lava, spread over the southern part of the district, plunged down the valley Laxárdalur and flowed almost to the sea.

The third volcanic cycle began with the Mývatnseldar [ˈmiːˌvasːˌɛltar̥] eruptions in 1724–1729 which commenced with an explosion that formed the crater lake Víti [ˈviːtɪ].

A few rhyolite mountains border the Krafla central volcano (Hlíðarfjall [ˈl̥iːðarˌfjatl̥], Jörundur [ˈjœːrʏntʏr̥], Hrafntinnuhryggur [ˈr̥apn̥ˌtʰɪnːʏˌr̥ɪkːʏr̥]).