New Zealand earthquake

17 Nov 2016

At ... is about the threat of tsunamis from earthquakes while at ... the focus is on the earthquake itself, magnitude 7.5 - and a plate boundary situation is being blamed (and the inevitable subduction zone). However, it was not as simple as that it would seem as lateral slop on a strike-slip fault is also involved - and a thrusting within the Pacific plate (close to the epicentre). In other words the epicentre of the earthquake was not at the plate boundary (or a subduction zone). The earthquake also triggered liquefaction in sediments (geologists have their own lovely choice of words to describe things) and landslides. The link points out the earthquake occurred on the eve of the Super Moon (the closest the moon has been to earth for 68 years). Obviously this is enough to get conspiracy theories spreading but in this instance it refers to a dispute between geologists - how much influence does the tidal reach of the moon have on the crust of the earth and can it cause earthquakes on occasion.

An upside down explanation is advanced at ... as upwelling magma is naturally considered to be the trigger to under the sea volcanoes (or that is the mainstream line of thought). This study is unusual as it suggest the sea floor split open and allowed the magma to seep out. Can the sea floor crack and what might cause it to do that? We know that lava seeps out at mid ocean ridges - and is a basic tenet of Plate Tectonics - but can lava seep out of the sea floor anywhere else?

Meanwhile, on the subject of volcanoes and magma, over at ... geologists explore the role of volcanoes during mass extinction events.