Earth Sciences Department
The Photo/Time Scale includes a photo scale on one side and a geologic timescale on the reverse. The photo scale features a 10 cm scale with mm increments and a 4 inch scale with 1/8 inch increments. The timescale is modified after the 2018 ICS and the 2018 GSA timescales. The colours and map unit symbols follow those recommended by the USGS, 2006. All but a few lines of text are legible with the unaided eye. A handlens may be needed for some text. The card is 16 x 7 cm and printed on 22 mil white plastic with a matte finish to cut down on glare while photographing.