Understanding Earth’s insides

Colleen Dalton, a Post Doctoral Research Fellow from Lamont-Doherty Earth Observatory at Columbia University, visited the College last Tuesday to give a geo-physics lecture titled “Imaging inside the Earth: Implications for temperatures in the Mantle.”

Dalton’s research focuses on determining the temperature of Earth’s layers by using earthquake signals to understand the inside of the Earth. “We obviously can’t travel to the inside of the Earth, so I try to use seismic waves to understand what’s going on,” Dalton said. “It’s like trying to figure out how a car works without being able to look underneath the hood.”

Her work relies on attenuation, which “describes a reduction in the energy and intensity of a signal.” Attenuation is relevant to her research because seismic waves generated by earthquakes also attenuate.

Through her research, Dalton is trying to understand “what rocks make up the Earth’s interior, what composition these rocks have, and what temperature they’re at, and if any of these rocks are partially molten (magma).”

Dalton is particularly interested in “the energy that is lost as the waves permanently deform the rocks they travel through.” By comparing various charts from scientific observatories around the world, from the past to the present, Dalton hopes to improve on old studies of attenuation for the most precise answers.

The details of this attenuation depend on certain factors, according to Dalton, of which “most importantly is the temperature of the rocks through which the waves are traveling.” Hotter rocks cause the waves to lose a lot of energy.

Dalton said, “By mapping out where in the Earth waves lose a lot of energy, and where they only lose a little bit of energy, we are really mapping out the temperature inside the Earth. Since the Earth’s interior is inaccessible to us – contrary to what the movie “The Core” tells us – These indirect measurements of temperature provide the best information about deep inside the planet.”