This project has focused on studying how mid-ocean ridges move over geologic time and what that means for the source region of erupted lavas on the seafloor. The Earth’s surface layer, the crust, is broken into many tectonic plates that move with respect to one another over millions of years. Where two tectonic plates separate from each other, mid-ocean ridges form. These seafloor volcanic mountain chains continually create new crust - 21 cubic kilometers per year, or about ⅓ of the volume of the most voluminous mountain in the world, Mauna Loa in Hawaii. They also drift across the surface of the Earth over time in a process called migration. This happens due to the collective motion of all the plates on a spherical globe, coupled with the fact that there are differences in density in the upper Earth layers. Understanding mid-ocean ridge migration is important for our understanding of plate tectonics on Earth, which subsequently ties into many other key topics, such as climate change and carbon cycling, the presence of water on Earth, geohazards like earthquakes and volcanic eruptions. 

Other methods have struggled to simulate this process, namely because our computing abilities still lack for such a complex problem, but also because data collection and physical observations are so difficult to obtain for such a remote part of the Earth. For this work, we have used a scaled laboratory model that is capable of mimicking a migrating mid-ocean ridge. This works by dragging (the migration component) a set of conveyor belts (which act as the tectonic plates) over the surface of a tank full of viscous corn syrup (representing the Earth’s second layer, the mantle). We analyze time-lapse movies taken during experiments and track tiny beads in the syrup to find patterns in the speed and direction of the flow. 

A key finding is that ridge migration fundamentally alters where mantle is drawn to the ridge from. By performing approximately 120 experiments, we have been able to simulate how the mantle flows in 3-D over ~50 million year timescales beneath a mid-ocean ridge. We compare experiments with a stationary ridge to experiments with a migrating ridge, and we assess how the migration speed and direction influence the resulting speed and direction of flow.    the source region in the mantle for newly erupted lavas at mid-ocean ridges is much shallower than was previously thought. Instead of sourcing rock thousands of kilometers directly beneath the ridge, our work shows that rock is sampled from shallow depths and from across large horizontal areas. This finding relates to how we interpret the layering and composition of the Earth’s interior.

We also look at how heating from the Earth’s core causes hot pulses of mushroom-cloud shaped material to rise towards the surface. These features, called plumes, rise through the mantle because they are less dense than the surrounding rock, but they are also incredibly sensitive to the mantle flow of that surrounding rock. In our experiments, we show that plumes are distorted when a ridge migrates over the top, causing hot plume rock to erupt to either side of the mid-ocean ridge. In fact, the faster the mid-ocean ridge migrates, the more deformed the plume becomes and the less likely it is to cause volcanic eruptions at the surface.

Over the course of this project, we have had as many as 300 visitors to the lab per year. Some of the key facts that we have found to be most interesting for guests are as follows:

• Tectonic plates can crash into one another, move alongside one another, or separate from one another. In the Atlantic ocean where the plates separate from one another, the entire ocean basin is actually getting wider over time.

• Mid-ocean ridges create new seafloor at roughly the speed at which your fingernails grow, so this is a very slow process!

• The entire underwater mid-ocean ridge volcanic mountain chain is long enough to wrap around the Earth twice.

• Corn syrup is very viscous, which means that it’s gooey and doesn’t want to flow as easily as (for example) water. Rock inside the Earth moves over millions of years, so it’s a lot like a viscous fluid. This is the basis for our experimental setup.

• When these mid-ocean ridges migrate (or drift) across the surface of the Earth, it’s a little like dragging a vacuum cleaner over a thick shag carpet. If the vacuum cleaner is held in one place for a long time, it can suck up dirt buried deep inside the carpet. But if the vacuum cleaner is moved around, it sucks up dirt only from the surface of the carpet, and over a much larger area. Of course mid-ocean ridges aren’t really “sucking up” mantle rock to make new seafloor, but you can think of our findings similarly.

Last Modified: 12/12/2022
Modified by: Christopher R Kincaid