dc.rights.license | CC-BY-NC-ND | |
dc.contributor.advisor | Hoek, W.Z. | |
dc.contributor.advisor | Drury, M. | |
dc.contributor.author | Visser, M.P.E. | |
dc.date.accessioned | 2012-05-08T17:00:54Z | |
dc.date.available | 2012-05-08 | |
dc.date.available | 2012-05-08T17:00:54Z | |
dc.date.issued | 2012 | |
dc.identifier.uri | https://studenttheses.uu.nl/handle/20.500.12932/10372 | |
dc.description.abstract | Every volcano erupts ash that is characteristic for that volcano. When tephra is produced, prevailing
winds can transport the tephra over large distances, where they are then deposited due to
gravitational and/or precipitational fallout. The goal of this paper is to detect and chemically analyse
middle to late Holocene cryptotephras in the Netherlands and trace these tephras back to their source.
The Rheinberg and Zijderveld cores are sampled and a separation method based on heavy liquid
separation was adapted for use on clay-rich material. Instead of ashing the samples in a furnace,
which would result in producing bricks from the clay, H2O2 is used to dissolve all the organic material.
The material is then subjected to heavy liquid separation. The particles remaining were then analysed
with the optical microscope and a tephra shard count was done. The particles were deemed tephra
based on their morphology and optical properties. However, after chemical analysis using the SEM, all
of these supposed tephra particles turned out to be biogenic silica or mica. No Icelandic tephras were
present. The biogenic silica was mistaken to be tephra due to its tephra-like morphology and the same
optical properties. The absence of tephras can be explained in three possible ways: 1) the ashcloud
did not extend as far as the Rheinberg and Zijderveld localities, 2) the deposition occurred by wet
fallout and since there was no precipitation in the Netherlands there was no tephra deposition and 3)
the localities were not suitable for deposition of tephra due to the possible presence of running water. | |
dc.description.sponsorship | Utrecht University | |
dc.format.extent | 4329623 bytes | |
dc.format.mimetype | application/pdf | |
dc.language.iso | en | |
dc.title | Detection of middle to late Holocene Icelandic cryptotephras in the Netherlands: tephra versus biogenic silica | |
dc.type.content | Master Thesis | |
dc.rights.accessrights | Open Access | |
dc.subject.keywords | tephra, biogenic silica, Hekla, tephra separation, particle morphology | |
dc.subject.courseuu | Geology | |