1.   Echoes from these pulses are bounced off of sub-seafloor rock layers and picked up by the hydrophones, which transmit information about potential oil reserves to computers for interpretation.

2.   It provided a detailed blueprint to the underground rock layers, indicating a previously undiscovered gas field that, without the seismic data, Pew would have missed.

3.   The Martian hills photographed by the Pathfinder camera show evidence of sedimentary rock layers and wide hillside ledges like the sides of lakes where long-standing water had evaporated.

4.   The rock layers involved are still covered by soil and vegetation, making them almost impossible for geologists to study.

5.   The rock layers were then raised, forming relatively high, flat surfaces.

6.   While doing some mapping work for a mining company, Buick and a colleague stumbled across a boundary between two rock layers that were not parallel.

7.   Explosions inside volcanoes occur when magma builds enough pressure to burst through rock layers and push closer to the surface.

8.   Rubidge said the fossil was found between two rock layers that had been dated by isotopic analysis of volcanic ash and other materials.

9.   The researchers recently re-examined the tools and used new tests to more precisely date them, including measurements of changes in the magnetic properties of the surrounding rock layers.

10.   Volcanologists said, though, the earthquake could weaken rock layers below Mayon and allow more magma to burst through to the surface,