flicker

var viewer = new Cesium.Viewer('cesiumContainer', {
		baseLayerPicker : false
	});

var usgs = new Cesium.ImageryLayer(new Cesium.WebMapTileServiceImageryProvider({
			url : 'http://basemap.nationalmap.gov/arcgis/rest/services/USGSShadedReliefOnly/MapServer/WMTS',
			layer : 'USGSShadedReliefOnly',
			style : 'default',
			format : 'image/jpeg',
			tileMatrixSetID : 'default028mm',
			maximumLevel : 19,
			credit : new Cesium.Credit('U. S. Geological Survey')
		}));
usgs.imageryProvider.readyPromise.then(function(){
	viewer.imageryLayers.add(usgs);
	toggle();
});

function toggle() {
	setTimeout(function () {
		usgs.show = !usgs.show;
		toggle();
	}, 500);
}