Puerto Rico Meta-Data Information about data: This data was collected in the Mameyes watershed located within the Luquillo Critical Zone Observatory in Northeastern Puerto Rico during the time period of June 11-21, 2013. Overall data collection was led by Doug Jerolmack, Timi Szabo, and Kim Miller. Timi oversaw the axis and equilibrium measurements, while Kim oversaw the image collection. All three contributed to site selection. Additional field assistance was provided by Colin Philips, Joel Johnson, and Gerard Salter. The data is arranged by the following columns: 1: Picture Number 2: Site 3: Watershed 4: A 5 B 6: C 7: Stable 8: Unstable 9: C/A 10: B/A 11: mm/pix 12: Area 13: Perimeter 14: Circularity 15: Roundness 16: Curvature Mean 17: Curvature Std Picture Number: This number is associated with the jpeg file containing the image of a single pebble on a red board. The numbers are given by the camera in sequential order with full file name "image_####.jpg". Zeros precede the number if it is less than four digits. Site Number: This number refers to the site location where the data was collected. The number is composed of the date and the sequential data collection site for that date. Example: Site 061113_01 refers to the first site collected on June 11, 2013. An easy numerical code has been assigned to each site for referencing in scripts. 061213_01: 1 061313_01: 2 061413_01: 3 061413_02: 4 061513_01: 5 061613_01: 6 061613_02: 7 061613_03: 8 061713_01: 9 061713_04: 10 061813_01: 11 061813_02: 12 061913_01: 13 061913_02: 14 062013_01: 15 062013_02: 16 062013_03: 17 Watershed: This string value refers to the name of the watershed the data collection site is part of. For this study there are two values: Bisley and Mameyes. Bisley is a small headwater watershed and is a tributary to the larger watershed of the Mameyes. Mameyes: 1 Bisley: 2 A: This is the long axis of the pebble measured in mm. This value was measure by Timi in the field using a tape measure. B: This is the intermediate axis of the pebble measured in mm. This value was measure by Timi in the field using a tape measure. C: This is the short axis of the pebble measured in mm. This value was measure by Timi in the field using a tape measure. Stable Equilibrium Points: Stable equilibrium points are points where the pebble will sit at rest as the net force acting on the pebble at this location is zero. However, if the pebble is knocked from this location, it will return to the stable position. It is a local minimum of curvature. These values were measured in the field by Timi. Unstable Equilibrium Points: Unstable equilibrium points are points where the pebble will sit at rest as the net force acting on the pebble at this location is zero. However, if the pebble is knocked from this location, it will not return to the equilibrium position. It is a local maximum of curvature. These values were measured in the field by Timi. B/A: This value is the axis ratio of the intermediate axis to the long axis and is a measure of the elongation of the pebble. This ratio is calculated using the hand-measured values of each axis from field measurements. C/A: This value is the axis ratio of the short axis to the long axis and is a measure of the flatness of the pebble. This ratio is calculated using the hand-measured values of each axis from field measurements. mm/pix: This number denotes the scale at which each picture was taken. It was measured using the matlab script 'mm2pix.m'. This script measures the distance in pixels between two points selected 100mm apart in each image. Area: This number is the area measured in pixels of the two-dimensional projection of the pebble from the images taken in the field. It is calculated in ImageJ using the "Analyze Particles" command, which determines the value by summing the number of pixels that are black in the binary image of the pebble (white background with balk pebble). Perimeter: This number is the perimeter measured in pixels of the two-dimensional projection of the pebble from the images taken in the field. It is calculated in ImageJ using the "Analyze Particles" command, which determines the value by summing the number of pixels along the black-white boundary in the binary image of the pebble (white background with balk pebble). Circularity: This value is a bulk shape parameter measured from the binary images using ImageJ. The ImageJ software states that this parameter is 4π*area/perimeter^2. A value of 1.0 indicates a perfect circle. As the value approaches 0.0, it indicates an increasingly elongated shape. Values may not be valid for very small particles. Roundness: This value is a bulk shape parameter measured from the binary images using ImageJ. The ImageJ software states that this parameter is 4*area/(π*major_axis^2), or the inverse of the aspect ratio. Curvature Dist. Mean: This number is the mean value of the curvature distribution. The local curvature of the pebble contour from the 2-D projected images are calculated on a 2mm length scale. Curvature Dist Std: This number is the standard deviation of the curvature distribution. The local curvature of the pebble contour from the 2-D projected images are calculated on a 2mm length scale.