Shea Burns

September 29, 1999

UNVR195A-011

Sea Floor Spreading, Lava Lakes, and Patterns

Patterns can be found everywhere in nature. Just take a look around, patterns can be seen in leaves, tree branches, snowflakes, animals, waves, fluids, and grains just to name a few. Some patterns are obvious, like the stripes on a zebra, the ripples of sand on a beach, or the symmetry in a snowflake. Other patterns are not so apparent, such as cracks in mud, the branches of a tree, or the shapes in clouds, but they can be seen with a trained eye. One particularly interesting example of an obscure pattern is that formed by geological faulting. One reason it is hard to find patterns in faulting is the enormous amount of time it takes to form the patterns. Recently, however, a correlation has been established between geomorphological patterns, as the faulting pattern is otherwise known, and "wax tectonics," as the Nonlinear Phenomena Group of the Laboratory of Solid State Physics at Cornell University calls it. These geomorpological patterns the wax model represents is that of transform faulting at plate boundaries in the ocean and the patterns formed in lava at lava lakes.

Before the details of the experiment, and even of the patterns found, an understanding of the geomorphological structure and its related faults must be achieved. Rifting, or spreading apart of two plates at the ocean floor, is also often called sea floor spreading. Sea floor spreading is exactly what it says, it occurs when two tectonic plates slowly move away from each other, creating a rift between them. This also causes transform faulting, where two plate boundaries are moving laterally in relation to each other. Hot liquid magma flows up into this rift from the molten core of the earth. As the magma moves up and cools it solidifies and creates new ocean floor. This is a fairly constant, but very slow process. The tectonic plates moving away from each other also cause transform faulting, where the two plate boundaries are moving laterally in relation to each other, rather than moving totally away from each other. The http://visearth.ucsd.edu/VisE_Int/platetectonics/seafloor.html web site has a more detailed analysis of sea floor spreading and a brief history of it. The pattern on the floor of the ocean now has taken the last 200 million years to form and is made of both the tranform faulting and the seafloor spreading(http://milou.msc.cornell.edu/wax/index.html).

The wax tectonics simulation, on the other hand, can be done very quickly. The simulation has a simple design. A tray is filled with paraffin wax. The tray is then heated from the bottom using heating coils or some other heat source to melt the wax, simulating the heat from the core of the earth. At the top of the tray is a fan blowing cold air across the top layer of the wax solidifying it, simulating the cooling and solidification the magma undergoes as it reaches the surface. Then, a board is pulled from the middle of the tray towards one of the edges creating the rift which the hot wax from underneath fills, modeling the actual tectonic plates moving apart from each other. A model of the setup is shown below.

As the wax is pulled apart it forms a zigzag pattern, and the faster it is pulled the more exaggerated the pattern. The Nonlinear Phenomena Group of the Laboratory of Solid State Physics, found at http://milou.msc.cornell.edu/wax/index.html, established that the pattern found in the wax model is also found in lava lakes. Another research group, found at http://flux.aps.org/meetings/BAPSMAR9 5/abs/SJ2012.html, describes the pattern as consisting of triangular segments. They state:

The Nonlinear Phenomena Group of the Laboratory of Solid State Physics, found at http://milou.msc.cornell.edu/waxtectonics.html, states that the wax simulation follows the motion of plate tectonics, but at slower velocities. At slow velocities, the rift formed remains in a straight line perpendicular to the forces forming the rift with faults parallel to the pulling forces. The rift formed in the wax model resembles the pattern formed by transform faulting of the earth’s crust. More specifically, it best resembles the specific type of transform faulting found at oceanic plate boundaries. When the velocity of the wax spreading in the model is increased, the quality of the pattern deteriorates in relation to the sea-floor spreading theory.

However, the pattern becomes increasingly similar to the zig-zag pattern seen in rift formations at lava lakes. The zig-zag pattern can be explained easily. Assume there are only 2 velocities in the model, the spreading rate velocity and the internal velocity of growth in the solidifying wax. When the speed of the spreading rate exceeds the speed of the wax growth in the rift, the rift must grow at angles to keep up. The angle, theta, will be the same as long as the difference in velocities is constant. The pattern and the angle theta can be seen below.

Patterns found in nature can be very interesting. Sea-floor spreading and the spreading of lava in lava lakes are just two examples of thousands that can be found. Sometimes seeing the patterns can be clear as crystal, and other times it takes a very analytical or even creative mind to put the pieces of a pattern together. Sometimes patterns can even be represented by a mathematical model or reproduced in a lab, like with the wax modeling, other times it cannot. Sea-floor spreading and lava lakes are great examples of some of the complex yet simple patterns found in nature, but they are not the only ones, so keep looking!!!