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Institutskolloquium - Archiv

Hier finden Sie eine Auflistung unserer Kolloquiumssprecher aus den vergangenen Semestern.

Winter Semester 2021/2022

Dresen
Prof. Dr. Georg Dresen

Titel: Seismic moment evolution during hydraulic stimulations in EGS projects-insights from lab and field tests

Kolloquium in Person

Zusammenfassung: tba

Herwartz
Dr. Daniel Herwartz

Titel: "Why are three isotopes so much more informative than just two? "

Seminar will take place in person. 

Zusammenfassung: Analyzing classic 18O/16O ratios (expressed as δ18O) in solids, liquids and gases has proven useful in almost every branch of earth science. Additional δ17O analysis generally help to better constrain the underlying fractionation mechanisms providing a more solid basis to quantify geologic processes. After explaining the basic theory, I will touch on several examples including: 1) the water cycle including basic concepts to constrain (paleo-)relative humidity and (paleo-)wind speed; 2) seawater temperatures on early Earth; 3) Snowball Earth; and 4) metabolic and enzymatic pathways in the phosphorous cycle.

Why are three isotopes so much more informative than just two?
Huppert
Dr. Kimberly Huppert

Titel: Storms, surf, & swells: Bedrock breakdown and the geodynamic demise of volcanic ocean islands

Kolloquium in Person

Zusammenfassung: With homogeneous bedrock, dramatic climate gradients, and remnant surfaces that constrain their age, initial topography, and vertical motions relative to sea level, volcanic ocean islands provide an exceptional natural experiment in landscape evolution. Analyses traversing gradients in island climate and bedrock age have the potential to advance our understanding of climatic and tectonic influences on landscape evolution in a diverse range of continental settings. Yet, as net subsiding and boundary-dominated landmasses, islands are in some ways dissimilar to most continental landscapes, and the mechanisms of island vertical motion remain largely enigmatic. Island uplift and subsidence can provide important observational constraints on the rheology and dynamics of the Earth’s interior, in addition to setting the boundary conditions for the topographic, climatic, and biogeographic evolution of island landscapes. In this talk, I exploit steep climate gradients in the Hawaiian Islands to quantify controls on fluvial and coastal erosion, and I assess the contribution of lithosphere and mantle processes to surface deformation at ocean hotspots. Through physically-based modeling, analysis of topo-bathymetric and geochronologic data, and field measurements, I examine (1) the control of rainfall variability on long-term rates of bedrock river incision on the Hawaiian Island of Kaua‘i, (2) the influence of wave power on bedrock coastal erosion in the Hawaiian Islands, and (3) the mechanisms that cause volcanic ocean islands to drown below sea level to form atolls and guyots. These analyses provide empirical support for hypothesized feedbacks between climate, tectonics, and topography, linking the evolution of the solid earth, hydrosphere, and biosphere. 

Azores
Santa Maria Azores
Liam Hoare
Dr. Liam Hoare

Titel: "Tales from Titanium: Isotopic insights into the crust-mantle system"

Seminar will take place in person. 

Zusammenfassung: Despite its relative infancy amongst the arsenal of stable isotope systems currently available for study, variations in the stable isotope composition of titanium (Ti) have received significant attention during the last few years. This stands in contrast to the long-established use of elemental concentrations of Ti in rocks and minerals as a tracer of magmatic processes. Ti is a refractory, lithophile (‘rock-loving’), highly insoluble element which possess a single valence state (Ti4+) under terrestrial conditions. Hence, Ti exhibits simpler chemical behaviour in comparison to other novel stable isotope systems, and thus it offers the promise of a less complex framework within which to interpret its isotopic variations. In most magmatic systems, the Ti budget is dominated by Fe-Ti oxide minerals (ilmenite, rutile, and Ti-magnetite) and as such isotopic variations in Ti are also primarily controlled by the appearance of these minerals during magma evolution. Following some basic introduction and background, I will cover the mechanics and controls of Ti isotopes in magmatic systems which will encompass three main topics:

  1. The behaviour and variation of Ti isotopes during magmatic differentiation across different tectonic settings (mid-oceanic ridges, intraplate volcanoes, and subduction zones) and an investigation of the controls of melt composition and magma water contents on Ti isotope fractionation
  2. The influence of different Fe-Ti oxide minerals (ilmenite, rutile, and Ti-magnetite) on the isotopic budget of Ti and the application of natural and experimentally derived mineral-melt Ti isotope fractionation factors to model various processes ranging from mantle melting

Using the enhanced quantitative understanding of Ti isotope variations gained from 1) and 2) will be applied to ascertain the efficacy of Ti isotopes as a novel tool to elucidate the tectonic setting of ancient volcanism, with a focus on the Oman ophiolite, the largest and best-preserved segment of oceanic lithosphere on Earth.

caption
Hoare
Cook
Dr. Kristen Cook

Titel: Fluvial disasters in the Himalaya - new insights and potential for early warning

Kolloquium in Hybrid format

Zusammenfassung: Natural disasters such as landslides, glacial lake outburst floods (GLOFs), and other catastrophic flash flood events are a major hazard in the Himalayas, and are a growing threat in a warming climate. Such events also have significant geomorphic impacts and may play an important role in Himalayan landscape evolution. While much work is focused on the initiation of extreme fluvial events, understanding their dynamics and downstream impacts is also important for evaluating both hazards and landscape dynamics. I will present observations from three recent fluvial disasters – a glacial lake outburst flood (Bhote Koshi, Nepal, July 2016), a rock/ice slide triggered flow (Chamoli, India, Feb. 2021), and a complex hazard chain (Melamchi, Nepal, June 2021). Each of these events had a different type of source and trigger, illustrating the difficulty of anticipating destructive floods in both space and time and highlighting the need for real-time detection and early warning of such events.

Cook Seminar
Anat Shahar
Dr. Anat Shahar

Titel: An Experimental Geochemistry View on Planetary Evolution

Kolloquium über Zoom

Zusammenfassung: One of the broader goals in Earth and planetary science is to understand the evolution of a planet from accretion to its present state. While each planet has a unique path, there are ubiquitous processes such as core formation, evaporation, and magmatic differentiation that can be studied in order to better understand planetary formation and evolution in general. In our current research we combine methods from stable isotope geochemistry and experimental petrology in order to enhance our understanding of these planetary scale processes. Experiments at high pressure and temperature simulate natural conditions within the Earth or planetary bodies, while stable isotopes can be used to show which physical and chemical processes natural materials have undergone. Each process that has occurred throughout the planet’s history has resulted in an isotopic fractionation of an element; the key is to understand the signal. This multi-disciplinary approach has been shown to be an effective way to study processes occurring at all conditions from the high-pressure metallic core of a planet to the low-temperature surface. In this talk I will synthesize what we have learned from experiments as well as compare our experimental results to terrestrial and extra-terrestrial samples. We find that stable isotopes are powerful tracers of planetary processes even at high temperature and pressure, and that experiments are the most effective way of unlocking the secrets within these tracers.

Diamonds
Bedford_Atacama_Desert
Dr. Jonathan Bedford (Atacama Desert Chile)

Titel: "Towards a continuous global tectonic monitoring system with Global Navigation Satellite Systems"

Seminar will take place in hybrid format. 

Zusammenfassung: Displacement data from Global Navigation Satellite Systems (GNSS; commonly known as GPS) have revealed many interesting geophysical phenomena over recent decades.  Some notable discoveries include:

- Continents are bobbing up and down, expanding, and contracting quasi-periodically in response to seasonal geophysical fluid loads on the Earth’s surface

- Faults are accommodating relative plate motion with a variety of slip behaviour that can be both seismic and aseismic

- Major earthquakes are causing sustained postseismic motions due to both on-fault afterslip and off-fault distributed deformation (flow)

- Earthquakes are sometimes preceded by accelerations in Earth surface displacement recorded at GNSS stations close to the epicentre

As the number of permanent tectonic GNSS stations worldwide grows, and as the length of time series at some of these stations now approaches multiple decades, we are increasingly able to recognize accelerations, both short- and long- term, related to a variety of tectonic and non-tectonic processes.  Furthermore, these transient plate motions can be local, occurring at one or a few stations, or broadscale, occurring over thousands of kilometres.  Significant challenges remain in isolating the tectonically related accelerations from those caused by geophysical fluid loading, while the non-linear interplay of fluid loading and tectonics is poorly understood.  Here, I will present a selection of case-studies spanning regional to continental spatial scales, in which novel transient features have become apparent.  I will show that subduction plate boundaries in Japan and Chile, home to some of the densest tectonic GNSS networks, are highly dynamic in between large earthquakes, with accelerations of the overriding plate occurring both towards and away from the trench.  Such motions hint at a variable interseismic subduction velocity that has implications for our understanding of various subduction zone processes.  I will also show examples of apparent interplay between tectonic systems – in which transient deformation on one fault system seems to be affecting subsequent deformation on nearby fault systems.  Finally, I will present an outlook for future research directions in tectonic GNSS, with a roadmap on how the community might best evolve from the current strategy (of providing retrospective case-study analyses) towards a future strategy that would allow for aseismic tectonic transients to be monitored in near real time.

Helmut Bock
Dr.-Ing. Helmut Bock

Titel: Das Fundamentale Kluftsystem

Hybrid format / Online über Zoom

Zusammenfassung: Klüfte in Gesteinen sind Dokumente bleibender Beanspruchungen. Sie sind in der Ingenieurgeologie und Felsmechanik von Bedeutung bei der Beurteilung des mechanischen Verhaltens Geologischer Körper, ebenso wie in der Strukturgeologie / Tektonik bei der Erfassung aktueller und Rekonstruktion fossiler Beanspruchungspläne.
Bei der Vielzahl von Klüften, die in der Natur zu beobachten sind, lässt sich eine Konfiguration herausfiltern, die den Grundtyp darstellt und als Fundamentales Kluftsystem
bezeichnet wird. Dieses System besteht aus zwei orthogonal zueinander stehenden Kluftscharen, wobei beide Scharen hinsichtlich Geometrie und mechanischer Eigenschaften
unterschiedlich ausgebildet sind. Es wird auf alternative Hypothesen zur Genese des Fundamentalen Kluftsystems eingegangen. Modellversuche und rezente Beobachtungen werden angeführt, die aufzeigen, dass es sich beim Fundamentalen Kluftsystem um Trennbruchflächen handelt, denen ein bestimmter Beanspruchungsplan zugrunde liegt.

 

Über Helmut Bock:

Geotechnischer Consultant, Bad Bentheim
Prüfsachverständiger im internationalen Geo-Ingenieurwesen.
- 2001 - 2007 Leiter der Fachsektion Ingenieurgeologie der DGGT und DGGV
- 1989 - 1998 Geschäftsführender Gesellschafter der Interfels GmbH, Bad Bentheim
- 1976 - 1991 Professor of Geomechanics, James Cook University, Townsville, Australien.
- 1976 Habilitation Ruhr-University Bochum
- 1972 Dr.-Ing. Institut für Bodenmechanik und Felsmechanik, Universität (TH) Karlsruhe
- 1965 Dipl.-Geol. Universität München.