The mystery of too-deep earthquakes

Look at the depth distribution of earthquakes on Earth (Fig. 1):

Fig. 1: Depths of earthquakes on Earth. Shallow earthquakes (0-60 km) are in red, intermediate-depth earthquakes (60-300 km) in purple and deep earthquakes (>300 km) in blue. Data from the International Seismological Centre.

In general, earthquakes are located at the boundaries between tectonic plates. Shallow earthquakes (< 60 km) happen at all plate boundary types, but intermediate (60-300 km) and deep (> 300 km) earthquakes mainly occur in subduction zones, where one plate moves beneath another. Because these earthquakes are located either within the subducting plate or between the two plates, they get deeper and deeper the further they are from the surface trace of the plate boundary. Because the plate located west of South-America moves towards the east and is subducted under South-America (Fig. 2), the earthquakes on the west coast of South-America get deeper from west to east (Figs 1, 2). Continue reading

Continued: The story of the deep carbon cycle…

… and the big black bear

Last summer, I was fighting my way through the boreal forests of Newfoundland in Canada, a place well renowned for its wildlife. Hence I was heavily armoured with big hammers, a huge can of strong pepper spray and some bear banger cartridges in my pocket, always smelling of mosquito repellent and making a lot of noise, in order not to surprise a sleeping black bear in the bushes. In the end, I didn’t need the bear spray or the cartridges, but every now and then signs of bears in our field area reminded us of their presence. And I took these safety measures much more seriously after we encountered a black bear close to a local landfill: you just feel small and vulnerable in front of such a huge, beautiful and elegant animal that is only 20 meters away from you, even if your car is just two meters behind you.

Fig1. Some of the wild life a geologist might need to be worried about.

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An ocean on land

Science is not all about books or laboratories, but also includes fieldwork. Unlike what people might think, this is not a holiday (although you get to bring home a lot of beautiful pictures) but work. And it is crucial for geology! But what do we do? And why? Standing in a beautiful landscape surrounded by rocks that contain information you are looking for, science shows a very different and adventurous side. Since our blog is about oceanic rocks, fieldwork can involve going on a ship. However, an ocean can be found also on land, and as we will show you in this movie, Oman hosts oceanic rocks with plenty of interesting features.

From the mountain to the lab

Sometimes as a geologist you get to travel and work in some pretty extreme locations. So how did I end up in a caravan halfway up a mountain over 300 km north of the Arctic Circle in Northern Norway, in a place only accessible by helicopter? Well, the most interesting rocks can often be in the hardest places to reach!

Arriving at the drill site, October 2014

My research is on a magma chamber formed deep down in the Earth’s crust 560 million years ago. As the magma crystallized, crystals settled and formed a series of layers that recorded the evolution within that magma chamber. Understanding these processes is central to my current research project. It just so happens that this fossil magma chamber is somewhere quite hard to reach. Continue reading

Fieldwork, the backstage

In the last two centuries, geologists devoted a lot of time and energy to extensive field studies, aiming to understand the evolution of Earth. Direct observation in the field of structures and relationships between different types of lithologies, units of rock determined by physical characteristics and composition, provide geologists with important information on the formation and shaping of our planet. Field geologists can expect plenty of time outdoors. A field geologist is a very curious person and from the start of their career will have an innate will to spend time in direct contact with nature. This inevitable feeling, also known as nature fever, often evolves into a need for scientific discovery. The more a geologist goes into the field, the more he needs to spend time in the field in the future.

Releasing pressure on the rock. A big hammer doesn’t break your back but breaks hard rocks. However, Val, safety first!
Releasing pressure on the rock. A big hammer doesn’t break your back but breaks hard rocks. However, Val, safety first!

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