Rocks to be Analyzed at UH, Could Solve Geology Debate
Researchers and students from the University of Houston are setting sail this month in search of “Godzilla.” Like the giant irradiated dinosaur of fictional fame featured in numerous films, this Godzilla can be found at the bottom of the ocean floor. But that's where the comparison ends.
Six UH students and Jonathan Snow, an assistant professor in the Geosciences Department, will take part in a four-week international expedition to explore a 10-million-year-old “tear” in the Earth’s crust. Nicknamed “Godzilla Mullion” because of to its size and its location south of Japan, it is more than 60 miles wide and is the largest known crustal tear worldwide.
Also known as an oceanic core complex, Godzilla Mullion formed when the normal oceanic crust – made of the volcanic rock basalt – is torn apart and deep crustal and mantle rocks, which are normally rare on the Earth’s surface, were exposed directly on the sea floor without their volcanic cover. What’s unique about Godzilla Mullion is not just its size, but also how quickly it formed.
“The normal rate is between 20 millimeters/year and 10 centimeters/year, though there are some faster and some slower,” Snow said. “We think Godzilla Mullion was spreading pretty quickly at about 80 millimeters/year before it stopped completely. The rate of spreading is one of the things we want to determine.”
Funded by a grant from the National Science Foundation and UH, Snow and his team will work with the University of Tokyo and the Japan Hydrographic Office to reach Godzilla Mullion. While his Japanese counterparts will use ultra sensitive equipment to measure magnetic anomalies and determine the exact spreading rate, Snow and his team will use tried-and-true methods to retrieve rocks from the 5-mile deep zone.
“Even in this age of manned submersibles and robots, both tethered and self-guided, the good old rock dredge is still our primary tool for studying the composition of the oceanic basement,” Snow said.
The rock dredge is a large steel scoop attached to a 5-mile long wire that is lowered to the ocean floor. After being dragged behind the ship, it returns to the surface with between 200 to 400 pounds of rocks. The large volume of oceanic rocks is expected to help solve a long-standing conundrum in the geoscience community.
“For a long time, certain rocks on land, known as ‘ophiolites’ have been thought to possibly originate in the same kind of ocean floor environment as Godzilla Mullion and to have been pushed up on land by tectonic forces,” Snow said. “But until now, we had very few lower crust and mantle samples from this environment to compare them with.”
The expedition will be divided into two two-week legs in August and September and will be led by Snow and one of his graduate students. The rocks will then be analyzed in the new laser ablation trace element laboratory at UH. The results of trace metal analyses of the rocks will help determine whether they are geochemically similar to ophiolites, and whether ophiolites can form in a similar environment.
“Everyone hopes that any gigantic, prehistoric creatures sleeping there don’t mind all the racket,” Snow said.