Seismic surface-waves may show amplitude resonances at certain frequencies depending on the thickness and elastic parameters of near-surface layers. We investigate if resonance frequencies of Rayleigh-waves, (seismic surface-waves polarized in the vertical plane) can be used to prospect archaeological remains of small-scale buildings such as pit houses. Our test site is a newly detected Viking age village on the island of Föhr (north Germany) where we concentrated on one typical pit house. The results from resonance analysis are compared with magnetic data, ground penetrating radar (GPR) and classical seismic refraction measurements. The method of Rayleigh-wave resonance mapping used in this paper is based on the idea that Rayleigh-wave oscillations on top of anthropogenic structures will show different resonances than on undisturbed soil. We perform spectral analysis of these oscillations to provide information related to the seismic site response. We process single vertical component recordings and map the change in resonance frequency that can be related to the archaeological objects. The test showed that the pit house can be mapped by Rayleigh-wave resonance analysis with a horizontal resolution of~0.6 m. Corresponding computations of the depth of the pit house agree with the results from GPR, magnetic modelling and refraction seismics. A modelling study helped to understand the connection between subsoil shear-wave velocity model and the signal generated by the pit house. The progress of seismic field measurement is slow compared to GPR and magnetometry. However, since seismic methods are based on elastic subsoil parameters, it can be applied in cases where magnetic contrasts are low or GPR fails because of high electromagnetic wave absorption.seismics (Models C, D, F to A, B, E), a change in topsoil velocity (Models E, F), a change in both velocities with the impedance contrast between the two layers kept constant (Model B) and a decrease in the velocity of the stiffer layer (Model C). The spectra show resonance frequencies at about 70 Hz for the Model 2 outside the pit house (Model D) and 45 Hz for Model 1 inside the pit house (Model A), which correlates well with the observation and thus supports the resonance frequency approach.The following effects can be observed: (a) Models A, B, C, and D show a strong maximum in the vertical component together with a sharpFigure 7. (a) Seismic shot gathers from the SH refraction reference profile (position see Figure 3). Picked first arrival times are indicated by blue and red dots. (b) Shear-wave velocity model obtained by the wavefront method. Numbers 1 and 2 indicate the two reference models that correspond to inside and outside the pit. For comparison, the measured magnetic signal of the profile and the location of the modelled prism are shown in (c). 2015. On the ability of geophysical methods to image medieval turf buildings in Iceland. Archaeological Prospection 22(3): 171-186.

Structures in Iceland were traditionally built of turf, earth and, to a lesser extent, stone. As turf was the primary construction material, the contrast in geophysical parameters between building ruins and surrounding soil is expected to be low. To investigate the extent to which the remains of turf buildings can be detected by geophysical measurements, we applied several geophysical techniques to a known turf ruin in southwestern Iceland. The methods used were magnetics, ground-penetrating radar (GPR), electromagnetic induction (EMI), electrical resistivity tomography (ERT) and seismic Rayleigh-wave resonance mapping (RRM). Magnetics identified an accumulation of stones inside and beside the ruin. The in-phase component of the EMI measurements, which can be related to magnetic susceptibility, showed the same pattern. A very precise image of the stones lining the inside of the former turf walls was generated by GPR. In contrast, EMI conductivity and ERT imaged the actual turf in the walls. Turf walls have lower electrical conductivity compared with the surrounding soil, probably as a result of different porosities. The mapping of Rayleigh wave resonance clearly revealed the outline of the ruin, as indicated by weaker amplitudes compared with the surrounding soil. Overall the results indicate that geophysical methods can be used for subsurface mapping of Icelandic turf structures and that the combined application of the methods maximizes this potential.

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ZusammenfassungDie moderne Welt ist gekennzeichnet durch eine fortschreitende Technologisierung und einen steten Wandel. Die damit einhergehenden Anforderungen lassen neue Fähigkeiten relevant werden. Diese häufig als 21st Century Skills bezeichneten Fähigkeiten umfassen unter anderem das sogenannte Critical Thinking. Der Begriff selbst entzieht sich dabei aber bisher einer einheitlichen und umfassenden Definition. Dieser Artikel verfolgt daher das Ziel, den Begriff Critical Thinking in seinen verschiedenen Facetten und Praxisausprägungen zu erläutern. Dafür werden zunächst Fähigkeiten und Fertigkeiten, die sich dem Critical Thinking zuordnen lassen, aus einer theoretischen Perspektive betrachtet, die Relevanz dieser Fähigkeiten in Bezug auf die MINT-Fächer herausgearbeitet und Querverbindungen zu verwandten Konzepten hergestellt. Ein anschließender Praxisteil illustriert an drei Beispielen, dass und wie Critical Thinking in konkrete Lernsituationen integriert werden kann. Insgesamt stellt dieser Beitrag damit ein Plädoyer dafür dar, Critical Thinking nicht als ein lästiges, auch noch zu beachtendes Unterrichtsziel zu verstehen, sondern vielmehr als einen integralen Bestandteil des MINT-Lernens der Zukunft.