The Impact of Megaslides on Tsunami Formation

The Impact of Megaslides on Tsunami Formation

Submarine slides are common triggers for tsunamis, especially when caused by factors such as earthquakes, volcanic activity, or sediment flux. Megaslides, however, are extreme versions of these underwater events that can have significant impacts on the surrounding areas. One such megaslide occurred in the Surveyor Fan in the Gulf of Alaska about 1.2 million years ago, making it the sixth-largest recorded megaslide in history. With an area of at least 16,124 square kilometers and a preserved volume of 9,080 cubic kilometers, this megaslide left a lasting mark on the region.

A recent study published in Geophysical Research Letters by Sean Gulick and colleagues delves into the details of this significant megaslide. By utilizing images from seismic reflection surveys and data from drilling efforts in the Gulf of Alaska, researchers were able to uncover the existence of the slide and study the changes in seafloor topography before and after the event. The study revealed that the onset of the Mid-Pleistocene Transition (MPT) between 0.6 and 1.2 million years ago played a crucial role in the occurrence of the megaslide. The shift in the glacial-interglacial cycles during the MPT led to increased sediment buildup and flux, causing slope instability in the region.

The researchers suggested that the combination of sediment accumulation and seismic activity during the MPT likely triggered the megaslide in the Gulf of Alaska. While seismic activity continues to affect the region, the occurrence of megaslides of the same magnitude has decreased significantly. This can be attributed to various factors, such as a change in the balance between sediment flux and seismic strengthening. The seismic activity in the region has caused sediment to compact, enhancing slope stability and reducing the likelihood of massive slides.

In addition, the presence of ice streams on the continental shelf has spread sediment deposits over a larger area, leading to less cohesive slides on the continental slope. The continuous buildup of sediment along the Alaska margin has also played a role in reducing the critical wedge taper, lowering the chances of slope failure in the region. Understanding the factors that contribute to megaslides and their implications for tsunami formation is crucial for mitigating risks and ensuring the safety of coastal communities in earthquake-prone regions.

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