These notes accompany our Geophysics and music episode of Academia Nut: Listen today at noon!

Selflessly and extensively compiled by Philip Heron, PhD Candidate in Geophysics

We welcome unsolicited submissions!

What is Geophysics?

Geophysics is the study of the earth and its many different processes. There are a fair few separate fields within Geophysics: Seismology (the study of the subtle shakings of the earth); Exploration seismology (finding oil and gas and minerals and everything under the earth); Gravity and Magnetics (study of the earth’s gravitational and magnetic field); Core dynamics (analysis of the spinning iron core, and what that does to the Earth); Geodynamics and plate tectonics (study of all things related to plates and mantle convection).

What do Geophysicists do?
...(apart from make playlists)?

The main provider of geophysics job is the energy industry. Note the use of the term energy industry, and not oil industry. There was a huge effort to change the thinking towards oil companies in the mid 2000s. It is true that oil companies like Shell, BP and Exxon are some of the largest contributors to the studies of renewable and clean energy research.

Within the energy industry you can work finding oil, gas and minerals, processing data for exploration, setting up surveys for deposits on land or at sea, or as part of the mining/drilling process itself.

Outside of industry, Geophysicists can work within the government as part of a Natural Resources department, or as part of a Hazard Analysis group (overseeing dangers within a country).

There is, of course, academia. This is especially true for those studying topics not related to the big money careers of exploration. I study pate tectonics at its birthplace (The Department of Physics in The University of Toronto). A man with a rather unassuming last name and a peculiar first name, Tuzo Wilson, helped pioneer the idea of plate tectonics (which is described below from a well written wiki article):

Plate tectonics is the idea that the rigid outer layers of the Earth (crust and part of the upper mantle), the lithosphere, are broken up into numerous pieces or "plates" that move independently over the weaker asthenosphere. Wilson maintained that the Hawaiian Islands were created as a tectonic plate (extending across much of the Pacific Ocean) shifted slowly in a northwesterly direction over a fixed hotspot, spawning a long series of volcanoes. He also conceived of the transform fault, a major plate boundary where two plates move past each other horizontally (e.g., the San Andreas Fault).

As a result of his painting donning the walls of my office, this playlist is heavily related to all things Tuzo.

American Geophysical Union:

The American Geophysical Union (or AGU) holds the largest Geophysics conference in the world – around 20,000 geophysicists from all fields coming from all corners of the Earth to discuss their findings and share ideas for a full week at the beginning of each December in San Francisco. Or at least the furthering of knowledge is the idea – free beer is served from 2-5 each day.

The very idea that all the leading Geophysicists would merge in an area prone to earthquakes baffles me. What if there was a huge earthquake, a kin to that of the devastating 1906, all of the people would could help or analyse the horrific natural disaster would be right up in the peril.

I am waiting for the day when people are able to accurately predict earthquakes. I’m imagining one day at the AGU when no earthquake seismologists turn up, leaving all the core dynamicists to perish.

Geophysics Playlist:

[Plate Tectonics!]

I study the formation and dispersal of supercontinents. As far as I know, there a very few songs about supercontinents, but a few that have plate tectonic leanings. Luckily, plate tectonics incorporate a lot of different topics.

A redistribution of landmass has an important effect on the spatial heterogenity of the Earth’s energy balance. This is controlled by the reflectivity of the Earth (albedo) and the thermal properties of the ocean and land. Clouds are the dominant force in reflecting energy, while continents are the most dominant absorber. The configuration of the oceans and continents (and ice sheets) affect the amount of energy attained from the sun.

In general, oceans are less reflective than continent, unless they are covered in ice. What happens when the continents are in different configurations? Or indeed all bundled up together to produce a supercontinent?

Supercontinents produce extreme temperature swings and desert-like dryness in their interiors and monsoons on their coasts. When there is a major convergence of continents like Pangea, cold winters and hot summers combine to produce a climate not suitable for glaciations.

From this supercontinent configuration of having all the land mass accumulated together, the plates move with the mantle below into their configuration today.

A must for any geophysics playlist is something from the magical land of Iceland. Sigur Ros is my chosen personification (sonification?) of the great island.

Starafur – Sigur Ros

Every song that Sigur Ros make is, for me, linked with the geophysics-dreamland of Iceland. The geology of Iceland is like nowhere else in the world. An island made relatively recently from the opening of the Atlantic Ocean, Iceland straddles the most eastern point of the North American plate, and the most westerly point of the Eurasian plate. It is the only country in the world that is comprised of two different plates. Full of volcanoes, spreading zones and everything else, Iceland is a must for anyone.

Transatlanticism – Death Cab For Cutie

The fascinating thing about what I study is that, even though we all have cultures and ideas that make us distinct as members of a country, the fact that many places are intrinsically linked together through being once joined; Scotland has the same land as eastern Canada, South American shares fossils with those in Western Africa. The Wilson Cycle describes the possibility of the cyclical formation of supercontinents. The formation of a mid-ocean ridge, like that seen in the mid-Atlantic, is a part of that process. Transatlanticism discusses at length, for 7 minutes, that process.

No Man Is an Archipelago – British Sea Power

Antartica can be thought of as an archipelago.

Modern Antarctica is characterized by glacial ice to depths of 3km in some places. 50Ma, despite occupying approximately the same position, the continent was covered in vegetation and forests and of a more hospitable temperature. 50-20Ma Antarctica separated from South America.

The passage widened and deepened, developing an Antarctic Circumpolar current (below).

This isolated Antartica from warm subtropical water and produced cooler Southern Ocean temperatures. It is possible that the current created conditions for a growth in life in the cold, nutrient-rich waters reducing CO2 levels and cooling the temperature on the continent further.

The opening of Drake Passage heavily contributed to the glaciation of Antarctica.

At this time, South American and North America were not attached. Plate tectonics closed up the Panama strait, leading to a land bridge which re-reouted ocean currents of two oceans. From there, the Gulf Stream was born! Warm Caribbean waters flowing towards England, the climate of NW Europe became warmer. The increased moisture was more readily available to be advected to high latitudes to produce growing ice sheets. These growing ice sheets then increased the albedo of the region, cooling the high latitudes.

The movement of plates, and their ability to influence glaciations, is therefore massively important to our climate and our wellbeing!

Fiery Ring – Appetite

YOU CAN DOWNLOAD THIS SONG HERE

The Pacific Ocean is getting smaller. In 80 million or so years it will be no more. Up until then there will be countless earthquakes and volcanoes of epic proportions, as we slowly stutter towards another supercontinent era. There are a lot of things I can talk about for the Ring of Fire...

Apart - Dappled Cities

Supercontinents are the coming together of continents. Now they are apart. Look at that, a tenuous link!

[Volcano!]

Volcanoes are a major contributor to climate change. This is not to say that human contribution to our fair Earth is insignificant, because it quite clearly is. A powerful Volcano, however, has the potential to wreak havoc very quickly. The eruption of Mount Tambora in 1815 generated enough volcanic dust to cover the globe, leading to the ‘Year Without A Summer’. Crops were decimated and the climate was significantly modified all over the world.

A recent study from the AGU has been reported in the BBC. Using new mapping techniques, the University of Durham and Oxford University in the UK has shown underwater volcanoes in the Pacific being subducted under the Eurasian plate. The surprising result is that as these volcanoes are subducted the earthquakes associated with the moving plate are surpressed, rather than more vigourous. The volcanoes are, apparently, softened up before suduction. Why or how this happens is not well known.

Volcano – PUSA

My brother had this album when I was growing up. At the time I thought the song was great. Maybe this influenced my desire to study Volcanic processes. But is there anything left to study in the field of volcanic processes that isn’t described in this song?

Vesuvius – Sufjan Stevens.

Sufjan from his recent album, The Age of Adz.

All Shook Up – Elvis Presley

“Her lips are like a volcano that is hot.” Elvis Presley = amateur geophysicist.

[Earthquakes!]

The topic of earthquakes I have decided to relate to Seattle and it closest danger – the Cascadian subduction zone.

The Cascadia subduction zone is part of the modern plate tectonic regime of the continental margin off southwestern Canada and Northwestern United States. The region is dominated by the interactions between three lithospheric plates: Pacific, North American and the intervening Juan de Fuca plate system (which includes the explorer, Juan de Fuca and Gorda plates). An extensive geological and geophysical data set off southwestern Canada has been generated over the past two decades making the Cascadia subduction zone one of the most comprehensively studied subduction zones in the world:

The Juan de Fuca plate is presently converging with the North American margin at a relative rate of 40 mm/yr. N56E.

The Explorer plate, a young fragment of the Juan de Fuca has been moving independently for 4Ma, is converging at variable rates along the margin. Estimated at 21mm/yr at N50E

Nootka fault zone, has estimated left lateral motion of approx 25 mm/yr.

There are not too many earthquakes occurring here, despite there being evidence for subduction. How do we know there is subduction? Well, folding and faulting are seen in seismic reflection images of sediments at the base of the continental slope. These sediments continue to be scraped off the underthrusting oceanic crust by the bulldozer blade of the continental crust. Another dramatic evidence for active subduction was the volcanic eruption of Mt. St. Helens in 1980, one of the chain of active (although some historically quiescent) arc volcanoes from northern California to southern British Columbia. The north-south extent of the volcanoes matches the extent of the subducting Juan de Fuca plate.

Cascadia arc volcanoes are limitied to the extent of subduction. The northern Cascadia subduction zone of western Canada lies between the underthrusting oceanic Juan du Fuca plate and the continental North American plate. Vertical and horizontal strain rates have been determined through long-term trends in tide gauge data, changes in repeated accurate levelling surveys, changes in repeated high accuracy gravity profiles and horizontal shortening observed by GPS and other precise positioning surveys.

Simple GPS surveys show that there is shortening of coastal regions and uplift in the surrounding areas (meaning the street level is slowly rising). These are two factors associated with a locked megathrust earthquake. These earthquakes do not release energy slowly and frequently (leading to small earthquakes very often), but blow off once in a while with a MEGA EARTHQUAKE. It is thought Cascadia moves with SILENT SLIP – as it causes very few earthquakes for how much it moves. Every time I hear that I think of this tune:

Silent Shout – The Knife

For a silent slip earthquake.

With the thrust fault locked, the 40 mm/yr convergence of the Juan de Fuca plate is taken up as elastic shortening across the continental margin. GPS measurements show Victoria to be moving landward at a rate of 7 mm/yr with respect to the stable North American continent.

Here is a schematic cross-section of the Cascadia subduction megathrust earthquake zone and the epicentres of some larger historical earthquakes.

The size of these historical mega-thrust earthquakes are enormous. And, they have the potential for huge tsunamis and inland flooding (the flooding, shown below is the only reason why we know that these earthquakes exist in the first places, as in the geological record the rocks show huge swampy areas occurring every 900 years or so).

Shalom of Safed – Citay

One of the bands I met during the Glocal Scene filming days. Citay are an 8-piece band from San Francisco. I am sure the constant shaking and swaying influences their Led- Zepplin-meets-the-Beach-Boys music. They are from SF, so therefore are in the shake, shake shake zone of the famous San Andreas Fault.

[Mountains!]

Snowdonia – Mechanical Owl

Mountains are formed by geophysical processes – either through plate shortening from subduction zones (Rocky Mountains), or through volcanoes, or both! Snowdonia is a mountainous area in Wales, UK with some spectacular views. Nothing like The Rockies, though.

The height of mountains help control climate and allow for cold air to reach high latitudes.

Landslide – Fleetwood Mac

In Canada, the number one natural hazard killer is avalanches/landslides. Landslides are very dangerous, especially when linked to large mountainous areas (volcanoes) and large bodies of water – as tsunamis can be generated.

[Gravity!]

Where Gravity is Dead – Laura Viers

Gravity is another area of Geophysics – the earth’s gravitational field is the 9.81 everywhere on the surface of the globe! The gravitational field varies due to the density structure of what is beneath it. Through studying the earth’s gravity we can find out a lot about our fair planet. A surface where gravitational potential would be zero is called a geoid. Here is wiki again:

The geoid is that equipotential surface which would coincide exactly with the mean ocean surface of the Earth, if the oceans were in equilibrium, at rest (relative to the rotating Earth), and extended through the continents (such as with very narrow canals). According to C.F. Gauss, who first described it, it is the "mathematical figure of the Earth", a smooth but highly irregular surface that corresponds not to the actual surface of the Earth's crust, but to a surface which can only be known through extensive gravitational measurements and calculations. Despite being an important concept for almost two hundred years in the history of geodesy and geophysics, it has only been defined to high precision in recent decades, for instance by works of Petr Vaníček and others. It is often described as the true physical figure of the Earth, in contrast to the idealized geometrical figure of a reference ellipsoid.

Finally... and this is a big one....

[Energy Industry Processing!]

This story is insane. When you work in geophysical industry – in the search of oil and gas, for example – you have to work with data that you, or a company, collect from the field. The data that you obtain is not really readable as is so you have to manipulate it, or touch it up, to make it possible to interpret. One of the techniques used is something called Auto-Correlation, where you take the original signal you used to obtained data (the clear, clean source signal) and try to match it with the garbled, stretched, and strained signals that you receive from your receiver. Does this entire story sound familiar to you musical folks? Well it should...

A geophysical signal processor, a job which I used to have, left the geophysics game in search of a career using his passion for music. What he invented, or was the first to use, was the process of auto-correlation with people singing. By taking the garbled voice of a singer and running an auto-correlation with the correct note that was meant to be sung, a geophysicists created Auto-Tune.

For better or worse, this exists. And Cher was the first, I think, to use it...

Believe - Cher

Science! Go see it, live, anywhere in the world!

Go find a science cafe near you There are also specific sites for world and Canadian sites at the bottom (because of course they have their own...)

In Seattle, you can check out: Science on Tap and Engage:Science

Let us know what you learn! -DJ Prismatic & the Academia Nut! Crew