Mount Broadshield, seen from Neðribrunnar. On the morning of 15 July 1841, after completing his ride around Skjaldbreiður (Mount Broadshield), Jónas sketched this general view of the mountain and its surroundings. The sketch was made at Neðribrunnar, some 11-12 kilometers WNW of Skjaldbreiður, and takes in about a dozen kilometers from left to right. On Skjaldbreiður's summit, 1060 meters above sea level, a low crater rim of jagged lava crust is clearly discernible; the crater itself is some 300 meters in diameter and 50 meters deep. The high ridge on the right is Skriða. The little tent-shaped object beneath it, low down on the south flank of Skjaldbreiður, is Karl.

Jónas wrote in his travel journal:

Skjaldbreiður is a circular mountain of medium height, sloping gently and symmetrically down on all sides. The gradient, wherever measured, was never less than 8° or more than 10-12°. The mountain is completely sheathed in lava [and] three major lava flows, i.e., three eruptions, can be distinguished.

[The second of these] is the great flow that ran to the south and southwest in a number of streams to form the vast Þingvellir Lava Field. Our country's earliest inhabitants had no real conception of its age. In the year 1000, when the Alþing was in session, news arrived that lava was erupting in Ölves near the home of Skafti Þóroddsson the Law Speaker.¹ Since a debate was in progress at the time about the urgent question of whether or not the country should adopt Christianity, the members of the heathen faction said: "No wonder the gods are showing anger over so insolent a change in faith!" To this Snorri goði replied: "Then what were the gods angry about when the lava flowed that we are standing on right now?" The heathens were at a loss for an answer; everyone knew this had occurred long before Iceland was settled by human beings.

All three of Skjaldbreiður's lava flows issued, without exception, from the summit of the mountain. No secondary crater appears anywhere on its flanks, whereas an enormous crater — without a cinder rim — is found at the top. I was not able to climb the mountain myself to study this crater. I know about it partly from the report of reliable informants, partly because I was able to examine it through my telescope: the snow that otherwise covers the mountaintop has not filled it up, with the result that its high lava rim towers up above the snow. (3D149-51)

Source: National Museum of Iceland (Þjóðminjasafn Íslands), Þjms. 12175 (digitally edited).