Jökull - 01.12.1983, Side 25

Laugahraun and Hrafntinnuhraun are similar, length of the fissures from which they were formed.
however, with no great diíference in the apparent
IGELANDIG TYPES OF CENTRAL central volcanoes. They have all formed over an
VOLCANOES extended period of time and contain lavas and
tephras which are basic, intermediate, and acidic
Figure 5 shows the three types of Icelandic in composition.
Fig. 5. Icelandic Types ofCentral Volcanoes (Composition includes basic, intermediate, and acidic rock
types).
NATURE OF VOLCANIC ACTIVITY ENVIRONMENT DURING FORMATION MULTIPLE FEEDER CONDUITS AND FISSURES
MIXED ACTIVITY Subaerial/ COMPOSITE CONE Stratified cone (stratovolcano) with summit crater Type: Snaefellsjökull
(Landforms resulting from flowing and airborne Subglacial COMPOSITE RIDGE Elongated stratified cone with crestal fissure and/or crater(s) Type: Hekla
material) COMPOSITE VOLCANO MASSIF Contains a single (or multiple) caldrea(s) Type: Dyngjufjöll
VOLCANO-LIKE LANDFORMS
IN ICELAND
Iceland also has volcano-like landforms, the
Pseudocraters, which, while not unique to Iceland,
are especially well represented by a diversity of
types at various locales in Iceland. Skútustadagíg-
ar is the type locality for such landforms, although
excellent examples of variations occur at Raudhol-
ar on the outskirts of Reykjavík (partly destroyed
as a quarry for road metal prior to ca. 1950 but
protected since that time), at Landbrotsgígar, east
of Kirkjubæjarklaustur, and northwest and north of
the Búrfell Hydroelectric Power Station along the
Fossá in Thjórsárdalur, to cite a few.
Fig. 6. Volcano-Like Landforms in Iceland.
NATURE OF VOLCANIC ACTIVITY ENVIRONMENT DURING FORMATION FORM OF FEEDER CONDUIT
TUBULAR CONDUIT (within a Lava Flow)
EXPLOSIVE ACTIVITY Subaerial* PSEUDOCTATERS Type: Skútustadagígar
* The prerequisite for the formation of pseudocraters is that the lava flows over terrain rich in ground
water, such as marshes (Raudholar near Reykjavík), waterlogged Sandur plains (Landbrotsgígar), or
over areas where clefts or cavities are more or less filled water (Skútustadagígar).
JÖKULL 33. ÁR 23