Geology topics

Sveinn P. Jakobsson

Publications and source records attributed to Sveinn P. Jakobsson.

4 recordsLinked to original sources

USGS2006

Study of volcano/ice interactions gains momentum

Observations of recent volcanic eruptions in Iceland and detailed studies of sub-glacially erupted deposits and the interaction of lava and pyroclastic flows with snow and ice have provided important new data that should lead to significant advances in the understanding of volcano/ice interaction on Earth and Mars. A conference on this subject, the first of its kind, recently brought together geologists, geophysicists, glaciologists, and planetary scientists studying various aspects of volcano-ice interaction.

Eos, Transactions, American Geophysical Union↗

USGS2000

Geological monitoring of Surtsey, Iceland, 1967-1998

Aspects of the geological monitoring of the volcanic island of Surtsey 1967-1998, are described. A hydrothermal system was developed within the tephra craters in late 1966 to early 1967. Temperatures in a drill hole, situated at the eastern border of the hydrothermal area, indicate that the hydrothermal system at that site has been cooling at an average rate of ≤ 1°C per year since 1980. The tephra was altered rapidly within the hydrothermal area, producing the first visible palagonite tuff in 1969. A substantial part of the tephra pile above sea level was probably converted to tuff by 1972. The visible area of tuff has gradually increased since then, primarily due to erosion of tephra at the surface. By 1998 52% of the exposed tephra area had been converted to palagonite tuff. By volume, however, some 80-85% of the tephra pile above sea level has been converted to tuff in 1998. The area of Surtsey has shrunk from its original 2.65 km 2 (1967) to 1.47 km 2 (1998) due to marine abrasion. The geological formations on Surtsey have, however, responded quite variably to erosion. The tephra pile was easily eroded, but marine abrasion. The central core of palagonite tuff is estimated to be ≤0.39 km 2 . Statistical estimation of models of the decreases of Surtsey indicate that it will last for a long time. The numerical experiments indicate that it will take over 100 years until only the palagonite tuff core is left. It is postulated that the final remnany of Surtsey before complete destruction will be a palagonite tuff crag, comparable to those of the other islands in the Vestmannaeyjar archipelago.

Surtsey↗

USGS2000

Volcanism and ice interactions on Earth and Mars

Volcano/ice interactions produce meltwater. Meltwater can enter the groundwater cycle and under the influence of hydrothermal systems, it can be later discharged to form channels and valleys or cycled upward to melt permafrost. Water or ice-saturated ground can erupt into phreatic craters when covered by lava. Violent mixing of meltwater and volcanic material and rapid release can generate lahars or jokulhlaups, that have the ability to freight coarse material, great distances downslope from the vent. Eruption into meltwater generate unique appearing edifices, that are definitive indicators of volcano/ice interaction. These features are hyaloclastic ridges or mounds and if capped by lava, tuyas. On Earth, volcano/ice interactions are limited to alpine regions and ice-capped polar and temperate regions. On Mars, where precipitation may be an ancient phenomenon, these interactions may be limited to areas of ground ice accumulation or the northern lowlands where water may have ponded fairly late in martian history. The recognition of features caused by volcano/ice interactions could provide strong constraints for the history of volatiles on Mars.

Book chapter↗

USGS1976

Geothermal flux through palagonitized tephra, Surtsey, Iceland: The Surtsey temperature-data-relay experiment via Landsat-1

The net geothermal flux through palagonitized basaltic tephra rims of the Surtur I and Surtur II craters at Surtsey, Iceland, in 1972, is estimated at 780 ±325 μ cal cm -2 s -1 , indicating a decline since 1969 when a flux of 1,500 μ cal cm -2 s -1 was estimated. Heat flux in this range characterizes the postvolcanic environment on Surtsey in which the subaerial palagonitization of basaltic tephra is associated with mass transfer of hydrothermal vapor, either of meteoric or sea-water origin, only a few years after cessation of eruptive activity. The flux estimation is the result of the Surtsey data-relay experiment via Landsat-1 which was carried. out in several phases. Successful field installation and test transmissions demonstrated the feasibility of repetitive long-distance (that is, 4,800-km) data transmission and reception from a volcanic environment in Iceland via the Landsat Data Collection System. Temperature data were transmitted for a 38-day period in November and December 1972. A near-surface vertical gradient of 69.4 °C/m was obtained, suggesting a mixed mechanism of heat transfer, partitioned between conduction and convection. Comparison of four methods for estimating fluxes between 500 and 1,500 μ cal cm -2 s -1 , using temperature data derived from the Data Collection Platform, suggests that, where the only temperature available are from the surface and a depth of 1 m, methods of estimating the net geothermal flux from examination of spectral radiance are superior to methods that assume dominant convection or conduction. A computerized thermal-modeling technique to construct parametric diurnal surface-temperature curves is particularly applicable. Flux-estimation methods that assume dominant convection or conduction are limited by the lack of temperature data at greater depths and lack of knowledge of the exact energy partition.

Surtsey↗