Page 73 - Fundamentals of Physical Volcanology

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50 CHAPTER 4

(a)
200
E E I
I
100 I I
Tilt (mrad) 0

–100
–200
A S O N DJ F M A M J JA S O N DJ
1976 1977

(b)
2
Elevation change (m) 1

0
A S O N DJ F M A M J JA S O N DJ
1976 1977

(c)
tilt and (b) surface elevation made
1.0 Fig. 4.7 Measurements of (a) ground
0.9 ∆ ∆ h
at Krafla volcano in Iceland during
h 0
1976–77. The timing and sense of
0.8 d
h the changes are perfectly correlated
0.7 showing that they have a common
source. Sudden deflation of the
0.6
h / h 0 ∆ 0.5 3.0 km summit and an inward tilt accompany
eruptive episodes (indicated by E)
∆ or intrusion (I) as magma leaves the
0.4 3.5 km
summit chamber. Part (c) shows
0.3 the results of fitting a Mogi model
to the uplift of the summit as the
0.2
chamber is recharged with magma
0.1 2.5 km between eruptions and intrusions.
(Modified from figs 3, 9 and 10 in
0
0 2 4 6 8 10 Bjornsson et al. (1979) Rifting of the
plate boundary in North Iceland
d (km)
1975–1978. J. Geophys. Res. 84,
3029–3038.)