window.onload = function () {
    var s = Snap('#glacialDates');
    Snap.load("https://fortress.wa.gov/dnr/geologydata/photos/web_images/ger_explore_glacial_dates.svg", function (f) {
        if (!f) {
            console.log('error loading radiocarbon image')
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            s.append(f);
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            var index = 1;
            var forward = s.select("#gdForward");
            var back = s.select("#gdBack");

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};