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Landslide triggers and types
Published in Jan Rybář, Josef Stemberk, Peter Wagner, Landslides, 2018
Robert L. Schuster, Gerald F. Wieczorek
Volcaniclastic deposits, particularly volcanic ash, often exist as loose, easily liquefiable materials, which when on steep slopes, easily can be triggered into debris flows with the addition of intense rain. Such volcaniclastic debris flows, which are referred to by volcanologists as lahars, have occurred on many volcanoes, with tragic consequences; two examples follow:
Sedimentary Petrology
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
Sedimentary rocks constituted of fragments of volcanic origin are called volcaniclastic rocks. These rocks contain the product of weathering and erosion of pre-existing volcanic rocks or pyroclastic debris. Pyroclastic is the name given to rocks composed of the ejecta from volcanic vents.
Zircon U–Pb age, whole-rock geochemistry and Nd–Sr–Pb isotope constraints on petrogenesis of the Eocene Zajkan gabbro–monzogranite intrusion, Tarom-Hashtjin magmatic belt, NW Iran
Published in Australian Journal of Earth Sciences, 2022
M. A. A. Mokhtari, H. Kouhestani, K. Z. Qin
In the Zajkan area, the major geological units are Eocene volcanic–volcaniclastic rocks (>2000 m in thickness; Hosseiny et al., 2016) that were intruded by the Zajkan intrusion (Figure 2). Volcanic rocks are andesite, trachyandesite and porphyritic andesite with local olivine basalt, andesitic basalt and rhyodacite lava flows (Hosseiny et al., 2016; Kouhestani et al., 2019a, 2019b). Andesites and trachyandesites comprise plagioclase, hornblende and biotite phenocrysts within fine-grained groundmass. Porphyritic andesite is composed of centimetre-sized plagioclase phenocrysts along with hornblende and minor small clinopyroxene phenocrysts set in a fine-grained to glassy matrix (Hosseiny et al., 2016). The olivine basalts consist of olivine, plagioclase, and clinopyroxene phenocrysts set in an intersertal and fine-grained groundmass (Hosseiny et al.,2016). Andesitic basalts show a porphyritic texture and consist principally of distinctive zoned phenocrysts of plagioclase and pyroxene (Hosseiny et al., 2016). The rhyodacite lavas are composed of largely plagioclase, sanidine, and quartz phenocrysts and rare biotite with a porphyritic texture (Hosseiny et al., 2016). The volcaniclastic strata is mainly tuff (i.e. crystal tuff, crystal lithic tuff, lapilli tuff, and tuff breccia), ignimbrite, agglomerate, sandy tuff and tuffaceous sandstone, with minor conglomerate intercalations (Hosseiny et al., 2016).