Matt Hoek

Advisor:  Dr. Brian Watson

SLU Festival of Science 2001 Poster Presentation

Scaling Analysis of Mid-Ocean Ridge Lava Flows

During the Spring of 1999, a team of scientists from the Lamont-Doherty Earth Observatory conducted a research cruise along the East Pacific Rise (17 28’ S latitude).  The scientists on the cruise were assisted by the underwater robot ABE, which stands for Autonomous Benthic Explorer.  ABE gathered a high-resolution data set as it tracked along the sea floor of the Rise, accurately mapping the topography of the bottom to within 10 centimeters.In addition to gathering navigation, latitude, longitude, heading, depth, and altitude data, ABE also took pictures of the lava flows on the sea floor with a camera mounted on its flotation device.

The goal of this analysis was to determine the multifractal and scaling properties of the lava’s visual reflectance field and to compare them to those of a similar study (Laferrière and Gaonac’h, 1999) conducted on reflectance fields of volcanoes at Mt. Etna and Mauna Loa.  While these two volcanoes are traditional cone volcanoes, the source of lava at the East Pacific Rise is a three kilometer fissure in the ocean floor.  There are several differences between the volcanoes at Mt. Etna and Mauna Loa and the mid-ocean ridge of the East Pacific Rise.  Because the ridge is about 2700 meters below sea level, the lava that floods out of the fissure is under extremely high pressure.  The lava is also quickly cooled by the surrounding seawater, which is at a temperature of  2°C.  Because the lava in our photos is produced by different flow mechanisms than the lava of Mt. Etna and Mauna Loa, we were interested to see how our results would compare to those of the 1999 study.

We first examined the scaling properties of several types of lava flows by performing Fast Fourier Transforms (FFT) on the digital images.  Our results were similar to the small-scale results from the study of Laferrière.  Preliminary results showed some interesting differences in the spectrum based on flow type.  For example, the talus morphology spectrum has an anomalous structure that we tentatively identify with the two-stage formation process of talus.  We also conducted a multifractal analysis of the images.  For each lava type, we hoped to find typical values of the universal multifractal parameters a and C₁, where a measures the degree of multifractality and C₁ measures the sparseness of the field.  The results of the multifractal analysis will be presented at the festival.