The Topography with Timeline and the Cities, Faults, and Topography with Timeline datasets contain KML TimeSpan markup, which assigns specific timespans to the various layers. The Time Slider can represent different times or timespans which make the appropriate layers visible. It appears when a dataset is loaded that contains time markup
The Google Earth Time Slider
Click the clock to set options for the Time Slider such as time zone, animation speed, and repeat mode.
The two range markers control the time range of the data displayed on the map.
The bar at the bottom of the range markers can be used to move them both in concert when they are together.
Each range marker can be moved independently.
The triangle that points to the right is the play button. When the animation is playing it becomes a stop button.