Jökull - 01.12.1980, Page 46

INTRODUCTION
The purpose of this paper is to present the
results of a detailed analysis of a fissúre swarm.
Fissure swarms are common in volcanic areas;
both in Iceland and in other volcanic regions.
In particular, the fissure swarms on Hawaii
have been described in detail (Duffield 1975).
They appear to be very similar to those in
Iceland, and are probably caused by the same
mechanism.
The one chosen for a detailed analysis is the
Vogar fissure swarm on the Reykjanes Penin-
sula. The peninsula is a continuation of the
Reykjanes Ridge and is important and inter-
esting as one of the few places where processes,
operating at sea bot-tom, might be seen on
land. The Vogar fissure swarm is one of the
major structural features on the peninsula and
therefore of great importance.
A geological map of the Reykjanes Penin-
sula is given in Fig. 1. The greater part of the
peninsula is covered by basalts of Holocene
age, but here and there older rocks crop out.
The Holocene volcanoes are of two types:
volcanic fissures and shield volcanoes. The
Vogar fissure swarm lies within one such
shield volcano, named Thráinsskjöldur.
The relevant previous work on the geology
of the Reykjanes Peninsula will now be briefly
outlined. Bernauer (1943) measured the total
Fig. 2. A map of the Vogar fissure swarm. (a) is fault, (b) is fissure and (c) is fracture
number. — Mynd2. Kort af sprunguþyrpmgunni við Voga, (a) er misgengi, (b) er sprunga og (c) er
sþrungunúmer.
44 JÖKULL 30. ÁR