Curiosity about the Earth is in MIT’s DNA—the seeds of the Department of Earth, Atmospheric and Planetary Sciences (EAPS) were planted in 1861 by geologist William Barton Rogers, MIT’s founder and first president, with Geology and Mining Engineering (Course IV) being one of the original six courses taught at MIT. In EAPS, our curiosity leads us to ask fundamental questions about our planet’s 4.6 billion year history—and its future. How did Earth come to be? What forces shaped it over time? And what sequence of events produced a world where life can thrive? Which mechanisms caused major environmental upheavals in Earth’s past? How can we meet humanity’s need for energy and natural resources while maintaining Earth’s habitability? Will we ever be able to predict earthquakes? Could we be approaching another mass extinction? Every day, EAPS scientists and students conduct discovery-driven research to understand the processes shaping our planet, investigating Earth’s deep interior structures, the forces that build mountains and trigger earthquakes, the climatic influences that shape landscapes and stir the oceans, and the conditions that foster life.
How do EAPS scientists conduct their research?
The Earth is our laboratory. Our students and faculty sail the oceans, fly into the clouds, and scale glaciers and mountains to observe and sample. Back in our world-class labs, we design complex experiments and computational models. Our research demands that we cross disciplines. Physics, mathematics, chemistry, and biology are all brought to bear in our investigation of the interconnected, overlapping systems that support life on Earth. Measurements of uranium and lead isotopes in Siberian volcanic rocks give us an elemental clock, pinpointing the eruption of 5 million cubic kilometers of lava over 252 million years ago and revealing a link to the demise of almost 90% of life on Earth. Past landslides inform computational models using soil depth, root strength, and pore water pressure to accurately predict future patterns and vulnerable areas. GPS and seismographic sensors deployed in the field enable detailed mapping to understand everything from large-scale mantle dynamics and tectonic activity all the way down to localized surface deformations and seismic events induced by man-made changes in subsurface reservoirs. And we combine lab experiments with computer simulations to help explain how fluids flow through the pores of rock structures deep underground—with implications for increased recovery of hydrocarbon resources, carbon sequestration, and the exploitation of geothermal energy.
EARTH IN THE NEWS
Jennifer Chu | MIT News
Plate tectonics have shaped the Earth’s surface for billions of years: Continents and oceanic crust have pushed and pulled on each other, continually rearranging the planet’s façade. As two massive plates collide, one can give way and slide under the other in a process called subduction. The subducted slab then slips down through the Earth’s viscous mantle, like a flat stone through a pool of honey.
For the most part, today’s subducting slabs can only sink so far, to about 670 kilometers below the surface, before the mantle’s makeup turns from a honey-like consistency, to that of paste — too dense for most slabs to penetrate further. Scientists have suspected that this density filter existed in the mantle for most of Earth’s history.
Now, however, geologists at MIT have found that this density boundary was much less pronounced in the ancient Earth’s mantle, 3 billion years ago. In a paper published in Earth and Planetary Science Letters, the researchers note that the ancient Earth harbored a mantle that was as much as 200 degrees Celsius hotter than it is today — temperatures that may have brewed up more uniform, less dense material throughout the entire mantle layer.
Pop Goes the Seafloor Rock
Helen Hill | EAPS News
MIT-WHOI Joint Program graduate student Meghan Jones studies seafloor lavas to reveal the inner workings of our planet. Using the human-occupied submersible Alvin and the autonomous underwater vehicle Sentry Jones has been exploring a surprising discovery: gas-filled volcanic rocks on the seafloor that "pop" when brought up to the surface.
Stream Network Geometry Correlates with Climate
Terri Cook | EOS News
Although dendritic river networks, whose branches join in treelike fashion to form increasingly larger streams, are found all over the world, the processes that shape them are still poorly understood. To explore whether climate influences the geometry of dendritic stream networks, Seybold et al. analyzed nearly 1 million digitally mapped river junctions in different climatic regimes across the contiguous United States.
Using the NHDPlus Version 2 database, which combines the best features of the National Hydrography Dataset (NHD), the National Elevation Dataset (NED), and the Watershed Boundary Dataset (WBD) and has a resolution of about 30 meters, the team calculated the angle between the average orientations of each stream and its tributary. They then averaged these junction angles across large hydrologic basins.
The results show that the branching angles vary systematically with climate, with a clear trend toward more acute angles (averaging 45°) in the most arid regions and wider angles (averaging about 72°) in more humid landscapes. This correlation, the researchers report, is found in all sizes of streams and is stronger than the relationship between branching angles and other factors, including topographic gradient and stream concavity, that have previously been proposed as major controls on stream network geometry.
Taking Earth’s Inner Temperature
The temperature of Earth’s interior affects everything from the movement of tectonic plates to the formation of the planet.
A new study led by Woods Hole Oceanographic Institution (WHOI) suggests the mantle—the mostly solid, rocky part of Earth’s interior that lies between its super-heated core and its outer crustal layer – may be hotter than previously believed. The new finding, published March 3 in the journal Science, could change how scientists think about many issues in Earth science including how ocean basins form.
“At mid-ocean ridges, the tectonic plates that form the seafloor gradually spread apart,” said the study’s lead author Emily Sarafian, a graduate student in the MIT-WHOI Joint Program. “Rock from the upper mantle slowly rises to fill the void between the plates, melting as the pressure decreases, then cooling and re-solidifying to form new crust along the ocean bottom. We wanted to be able to model this process, so we needed to know the temperature at which rising mantle rock starts to melt.”