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Saemundsson, K.

Thorarinsson, S.

Williams, R. S., Jr.

English

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SATELLITE GEOLOGICAL AND GEOPHYSICAL REMOTE SENSING OF ICELAND
Richard S. Williams, Jr.
U.S. Geological Survey
Reston, Virginia 22090
a%
S 15 December 1973
Special Report No. 3: Reprint of abstract of paper, "Vatnaj8kull
Area, Iceland: New Volcanic and Structural Features on ERTS-1
H Imagery," which was presented at the 1973 Annual Meetings of the
= 4 0 Geological Society of America, and published in Geological Society
0. Es of America Abstracts with Programs, 1973 Annual Meetings, v. 5,
Z K0 no. 7, October, p. 864-865.
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AIUAX I MIG;S, MnAAS, TEXAS 865
and volcanic features which are partly or wholly buried
under the icecap. Some of these features were previously
unknown or only suspected. The morphology of Bar6arbunga,
an area east of Hamarinn, and Esjufjll suggest buried cen-
tral volcanoes. Two elliptical features, one at Kverkfjll
and another at Esjufjll are recognized as probable sub-
glacial calderas. A line of depressions between Hamarinn
arid Grimsv5tn is related to subglacial geothermal or vol-
canic activity. The easternmost depression is related to an
August 1972 j6kulhlaup on the Skafta river. A chain of
shallow depressions E to SSE of Grimsfjall may show the
subglacial course of floodwater from the March 1972 j8kul-
hlaup from Grimsvdtn.
Two prominent volcano-tectonic lineaments can be traced
across the image. One strikes N.45'E. for at least 80 km
along a line of nunataks and subglacial volcanoes, calder-
as, and geothermal areas. The other volcano-tectonic line
strikes N:35'W. along Vatnajkull's southern margin, cut-
ting across the other alignment. This latter structural
feature separates two markedly different tectonic regimes.
On the southwest is an area dominated by volcanic fissures,
faults, hyaloclastite ridges, and crater rows of unusual
length and linearity. Northeast of this line, mostly with-
in, but also just beyond the margins of Vatnajdkull, is an
area dominated by central volcano complexes.
PRI;CE !ILLIA! SOUD, ALASUA, A VOLCA&OGUIC 1ASSIVE SULFIDE
PROVI.CC
Wiltse, !ilton A., Department of Geology, Colorado School of lines
Golden, Colorado 80401; !:cGlasson, J. A., Department of Geology
Colorado School of :ines, Golden, Colorado 80401
Recent studies indicate that the Prince William Sound, Alaska copper
deposits are strata-bound massive sulfides, not post-metamorphic
epigenetic vein deposits as previously reported. Host rocks consist
of turbidites, and subaqueous tuffs interbedded with pillowed basalts
of the Early Tertiary? age Orca Group. All rocks in the area have
been dynamothermallymetamorphosed to lowest rank greenschist facies
contemporaneous with or following cataclasis. Close spatial relation-
ship between the ore deposits and shear zones suggests an epigenecic
origin of the ores, but this relationship is misleading.
A volcanogenic origin of the ores is indicated by the following:
1. On Latouche Island, cataclastic ore textures, confinement of
ore to siltstone units, absence of post-metamorphic intrusions, lack
of hydrothermal wall-rock alteration, and absence of hydrothermal veins
provide evidence for the premetamorphic origin of the sediment-
(tclosed deposits.
2. On Knight Island, assymetrical distribution of Zn values with-
in lensoid ore bodies, confinement of ore to subaqueous-tuff units,
depletion of metals adjacent to spatially related shear zones, and
lack of hydrothermal wall-rock alteration show that the deposits found
interbedded with pillowed basalts are not hydrothermal veins.
Geological Society of America,
864 ABSTRPCTS WITH PROGP.AMS, 1973Ann . MtTies.Dallas, Texas, p. 864--865.
Following sti ilstand, Matagorda Island prograded Gulfward approximately
one mile. During this progradation, four large tidal passes, which
connected the Gulf of Mexico with the landward lagoon, were closed.
The island was further modified by erosion and reprogradation of the.
island's eastern end, as well as by migration of the southern pass
several miles to the west across the island's southern end.
The source of sand which makes up this barrier complex is two-fold.
Prior to stil stand, erosion of Pleistocene strand plain sand and
middle Holocene fluvial-deltaic sand which was exposed on the shelf,
supplied most of the sediment to the early barrier. Following still-
stand, with progradation, shelf sands were too deeply submerged to be
eroded by Gulf waves. Sand, discharged into the Gulf by the Colorado
and Brazos Rivers, and transported southwestward by longshore currents,
was deposited on the beach and Thoreface of Gulfward bui Iding
Matagorda Island.
BEAT LOSS FROM THE EARTH: NEW ESTIMATE
Williams, David L., and Von Herzen, Richard P.,
Department of Geology and Geophysics,
Woods Hole Oceanographic Institution,
Woods Hole, Massachusetts 02543
From analysis of observed heat flow values and incorporating mod-
ern tectonic models of sea floor spreading, the average heat loss from
the Earth's interior is calculated at 9.2 x 1012 cal/sec ( ±20%) or an
average of 1.8 x 10-6 cal/cm 2.-sec (HFU) over the Earth's surface. This
is about 20% larger than previous estimates. The principal source of
uncertainty derives from unknown parameters of the oceanic lithosphere.
The hypothesis of extensive hydrothermal circulation in young crustal
material near active spreading mid-ocean ridges3 is invoked to explain
why values measured by standard oceanographic techiques fail to de-
tect the total heat flux near these ridges. With the average contin-
ental heat flow of 1.5 HFU, and oceanic of 2.0 IU, the surface heat
flux is biased toward the southern (ocean) hemisphere. This does not
necessarily indicate long-term asymmetry in the cooling of the Earth.
Models of the Earth no longer need be constrained by the previously
accepted equality of ocean and continental heat flow. Rypotheses of
the thermal history of the Earth or the relationship between Earth and
chrondritic meteorite composition and heat production may be modified
by the new value. The Earth's heat loss is about 5 times the rate at
which man uses energy (2x10 12 cal/sec) and about 4000 times less than
the rate at which solar radiation impinges on the Earth and its atmo-
sphere (4x1016 cal/sec).
VAINAJ~KULL AREA, ICELAND: NEW VOLCANIC AND STRUCTURAL FEATURES ON
ERIS-1 IMAGERY
Williams, Richard S., Jr., U. S. Geological Survey,
Reson i i u ; ihorarinsson, Sigur6ur,
University of Iceland - Science Institute, 3 Dunhagi,
Reykjavik, Iceland; Samundsson, Kristjin, National
Energy Authority, 116 Laugavegur, Reykjavik, Iceland
An ERTS-1 image of the snowcovered Vatnajbkull area, Ice-
land, acquired at 7' sun angle, reveals large structural
.3


Satellite Geological and Geophysical Remote Sensing of Iceland. Vatnajoekull Area, Iceland: New Volcanic and Structural Features on ERTS-1 Imagery

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