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Satellite images are revealing the scale of the destruction in Sri Lanka caused by landslides triggered by Cyclone Ditwah at the end of November 2025.

At the end of November 2025, a “weak” tropical cyclone, subsequently named Cyclone Ditwah, formed just offshore from Sri Lanka. Over the following day the storm tracked around the south and east coasts of Sri Lanka before moving northwards to dissipate on 3 December off the east coast of India. This was not a strong tropical cyclone, but it brought catastrophic rainfall to Sri Lanka, triggering extremely extensive landslides and floods.

The stats on the impact of Cyclone Ditwah on Sri Lanka are horrifying. The UNDP is reporting that 1,200 landslides were triggered and that about 20% of the island was affected by flooding. As of the time of writing, there are 639 known fatalities, with a further 203 people reported to be missing. The highest loss of life occurred in Kandy District, in the hilly centre of of the country. Many of the fatalities occurred in channelised debris flows.

The impact of the storm is complex – to study the landslides properly would require a PhD study or similar – but a quick inspection of the Planet Labs imagery of the centre of Sri Lanka illustrates the scale of the devastation. This image, collected on 7 September 2025, shows an area in the vicinity of [7.43518, 80.87898]:-

A satellite image of part the area affected by landslides triggered by Cyclone Ditwah in Sri Lanka. This image shows the area before the event. Image copyright Planet Labs, used with permission, dated 07 September 2025.

This image, collected on 30 November 2025, shows the same area after the passage of Cyclone Ditwah:-

A satellite image of part the area affected by landslides triggered by Cyclone Ditwah in Sri Lanka. This image shows the aftermath of the event. Image copyright Planet Labs, used with permission, dated 30 November 2025.

And here is a slider to compare the two images:

Image copyright Planet Labs.

And here is the post event image pasted onto the Google Earth DEM:-

A satellite image of part the area affected by landslides triggered by Cyclone Ditwah in Sri Lanka. This image shows the aftermath of the event. Image copyright Planet Labs, used with permission, dated 30 November 2025.

In the foreground is a large landslide that has started at the ridgeline. It has entrained heavily along the track, and has impacted a large area of fields at the toe of the slope. Note the channelised debris flow close by. In the background are multiple shallow landslides, many of which have reached the drainage line to generate channelised debris flows. These have been devastating downstream.

The impact of these landslides will be long lasting. I have made the point before, but it is worth reiterating, that tropical cyclones are often associated with strong winds and storm surge, but a huge proportion of the damage is actually caused by rainfall. Cyclone Ditwah was, in meteorological terms, “weak”. The images above show that this is a completely inappropriate way to characterise such storms.

Acknowledgement

Images from Planet Labs 2025 – see: https://www.planet.com/. Thanks as always for their agreement that I can use their images on this blog.

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

New research reveals how the speed of ocean currents and the shape of the seabed influence the amount of heat flowing underneath Antarctic ice shelves, contributing to melting.

SummaryThe regional seismic travel-time (RSTT) model predicts travel times of regional seismic phases accounting for three-dimensional structure of the crust and the upper mantle on a global scale. Previous versions of the RSTT model have been implemented using nodes separated by ∼1° spacing across the globe. A regional-scale study using regional Pn and Pg travel times across Israel and the Middle East demonstrated that data driven, systematic grid refinement reduces travel time residuals and enhances resolution of smaller tectonic features in regions having dense ray coverage. High density Pn ray coverage in the western US, Europe, Middle East, and East Asia can likewise provide the resolution that allows systematic global grid refinement of the RSTT model. In this study, we use a large number of Pn ray paths originating from events located with an epicentral location uncertainty of 25 km (GT25) or better. We conduct targeted grid refinements at 1.0°, 0.5°, 0.25°, and 0.125° on a global scale, producing a refined RSTT model that yields a 21.6% reduction in median event location error in Europe and the Middle East, when compared with the original global RSTT model presented in Begnaud et al. (2021a). The new model also resolves finer tectonic structures in regions with high Pn ray density.

SummaryWe present and apply a pseudo trans-dimensional inversion method for 3D geometrical gravity inversion, in which the number of rock units, their geometry, and their density can vary during sampling. The method is designed for efficient exploration of the model space and to infer the presence and properties of units not directly observable but detectable with geophysical data. Sampling relies on a non-reversible Metropolis-Hastings algorithm, during which rock units can be added or removed from the model, interface geometries are perturbed using random fields, and densities are sampled from distributions informed by prior information. To visualise the space of sampled models and to aid interpretation, a workflow is proposed that combines dimensionality reduction with the clustering of models in families. The capabilities of the inversion method are evaluated using two synthetic cases. The first is a motivating example aimed at recovering an intrusion missing from the prior model. It features a horizontal layer-cake where fixed-dimensional inversion fails to adequately fit the data and sample models close to the true model, while the proposed pseudo trans-dimensional approach is much more successful. The second case investigates the recovery of two missing units and the capability to overcome prior model biases. Results show the potential of our method to infer the presence of unseen geological features such as intrusions. However, they suggest that with biased prior geological modelling, it may be challenging to infer with certainty the presence of more than two previously unknown rock units at depth.

SummaryWhen highly viscous fluids are present in a rock medium, the viscous effect of such fluids cannot be neglected in the propagation of elastic waves. In this paper, a fractional thermoporoelastic theory is newly proposed, which is a further improvement of the two-temperature generalized thermoporoelastic theory. Firstly, by introducing the Kelvin-Voigt model into the stress-strain constitutive equation, the viscous effect of highly viscous fluids is considered. Then, fractional derivatives are introduced into the heat conduction equations of the solid and fluid phase to consider the anomalous heat conduction caused by the viscous effect in rock media. Plane wave analysis method is adopted to obtain the phase velocity and attenuation factor of four longitudinal waves (P1, P2, T1, T2). Numerical results show that the introduction of fluid viscosity leads to the appearance of new relaxation peaks in the P wave at high frequencies, and the introduction of fractional derivatives causes a decrease in the phase velocity and attenuation factor of T waves. The results provide a reference for further research on the wave propagation in rock media containing highly viscous fluids.

SummaryInduced polarization (IP) effects in airborne electromagnetic (AEM) surveys have commonly been investigated in helicopter-borne systems, leaving both a bibliographic and application gap for fixed-wing configurations. This gap partly reflects the large relative number of helicopter compared to fixed wing AEM systems, but also the geometric complexity of fixed wing platforms. In these platforms, nine geometric parameters come into play: the pitch, roll, and yaw of both transmitter and receiver, plus the three-axis offsets between the coils. Shifts in these factors can distort the measured data in ways that aren’t uniquely attributable, making it hard to pinpoint whether negative recordings truly arise from IP or from geometry-related effects. The non-fixed geometry also complicates removal of the primary field, often requiring iterative processing steps that may suppress or alter spectral content linked to IP. With advances in airborne IP understanding from helicopter-borne systems, revisiting fixed-wing platforms is both timely and necessary. Part A of this two-part study addresses this issue using the TEMPEST™ fixed-wing system connecting numerical modelling with field evidence. A suite of synthetic two-layer models with variable resistivity and chargeability parameters was developed to evaluate the system’s sensitivity to polarizable structures. The experiments demonstrate that IP effects, including negative secondary field responses, can be reliably detected in fixed-wing AEM data, both in X and Z magnetic field components. The capacity of these systems to detect IP phenomena is, however, strongly dependent on the electrical conductance of the environment. For instance, both fixed-wing and helicopter-borne systems, elevated near-surface conductance enhances the amplitude of purely electromagnetic induction currents, which in turn can dominate the recorded response and obscure the comparatively weaker polarization currents. More in general, IP detectability depends on the strength of the EM response generated by induction currents flowing elsewhere, which can dominate the small reverse current flow from a polarizable target. This highlights the critical role of near-surface conductivity in controlling the expression of IP responses and underscores the need to carefully account for these factors when interpreting survey data. The synthetic results are then connected with field-scale observations from a subset of the AusAEM dataset, over 470 000 line-km of TEMPESTTM data, where negative responses align with areas of low shallow conductance, confirming the simulation results. These finding open the way to the Part B of this study, where TEMPESTTM data are inverted taking into account IP and compared with helicopter-borne results and geological information.

The Greenland and Antarctic ice sheets are highly vulnerable to global warming and scientists are being increasingly worried about the possibility of large parts of the ice sheets collapsing, if global temperatures keep on rising.

Galápagos is a living laboratory where every environmental decision matters. On Santa Cruz, the most populated island of the archipelago, freshwater is a limited and increasingly vulnerable resource due to urban growth, agricultural pressure, saltwater intrusion, and climate change. In this context, understanding how water behaves across the landscape becomes essential for water security.

What if it were possible to take a very slow geological process, one that takes thousands of years in nature, and speed it up so that it happens within hours, in order to slow the rate of global warming?

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Yueji Liang, Xingyu Zhao, Binglin Zhu, Xi Guo, Chao Ren, Xianjian Lu, Zhengzhou Feng, Jinlong Pan

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Izhar Ul Haq, Honghua Dai, Jiye Zhang, Liangjun Song

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Yuxiang Tian, Qinqin Liu, Wenxiu Liu, Wenjie Wang, Xuhui Shen

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): E.A. Zakharova, I.N. Krylenko, P.P. Golovlev, A.A. Lisina, A.A. Sazonov, N.К. Semenova, A.V. Kouraev

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Yueqian Shen, Chenyang Zhang, Jinhu Wang, Jinguo Wang, Junjun Huang, Yanming Chen

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Dan Yang, Xiaoning Su, Jiale Huang, Weifang Yang

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Ziliang Zhao, Xiaofeng Li, Haiyu Gu, Kangjia Fu, Cheng Wei

Publication date: Available online 2 December 2025

Source: Advances in Space Research

Author(s): Banding Wei, Zhicai Li, Wei Yan, Junli Wu, Zhiquan Zhang, Xiaoqing Wang, Lv Zhou

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

If you spin a bowling ball, the finger-holes will end up near the rotation axis because putting mass as far from the axis as possible minimizes energy. So, on planets –if there is a large mountain, it will end up at the equator; in physics terms, the axes of rotation and maximum inertia align.

Conversely, a planet that is very spherical will be rather unstable, so that the solid surface can move relative to the rotation axis, so-called true polar wander (TPW). Because of its slow rotation, Venus is extremely spherical; TPW can thus easily occur, driven for example by mantle convection, which is time-dependent. Furthermore, Venus’s axes of maximum inertia and rotation are offset, by about 0.5o.

In a new paper, Patočka et al. [2025] analyze the effect of convection on Venus’s axial offset and potential for TPW. They find TPW rates that are consistent with geologically-derived values, but that the resulting axial offset is much smaller than observed. Their conclusion is that atmospheric torques are likely responsible, as they probably are for the apparent variations in Venus’s rotation rate measured from Earth.

The angular offset between the rotation and maximum inertia axis as a function of time, driven by time-dependent convection. The mean value (0.0055o) is two orders of magnitude smaller than the observed value (0.5o). Convection cannot be causing this offset. Credit: Patočka et al. [2025], Figure 2e

Three spacecraft missions will soon be heading to Venus. Direct measurement of the effects predicted by the researchers are challenging, but the coupling between atmospheric dynamics and planetary rotation will surely form an important part of their investigations.

Citation: Patočka, V., Maia, J., & Plesa, A.-C. (2025). Polar motion dynamics on slow-rotating Venus: Signatures of mantle flow. AGU Advances, 6, e2025AV001976. https://doi.org/10.1029/2025AV001976

—Francis Nimmo, Editor, AGU Advances

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

The ocean is saturated with microplastics. While we know the location of the great garbage patches, where plastic particles may accumulate below the ocean surface remains unknown. The vastness of the ocean means particle sampling data are sparse, but modeling how particles aggregate in 3D fluid flows can help determine where to look.

Wildfires pose a significant threat across the southwestern United States, due to the region's unique topography and weather conditions. Accurately identifying locations at the highest risk of a severe wildfire is critical for implementing preventive measures.