Hold any mouse button down as you move the cursor across the large GOES-8 visible image; the smaller inset window shows the corresponding GOES-8 "split window" IR image. The split window IR product is created by taking the difference in brightness temperatures between the 10.7 micron IR and the 12.0 micron IR -- differences in the emissivity of silicate particles in the ash cloud lead to negative values in the split window IR product. The main portion of the volcanic ash plume (blue, yellow and red enhancement) can be seen spreading to the north and northwest (toward Mexico City, MMMX), with parts of the plume spreading to the south.