Google updated Ocean Expeditions layer in Ocean folder in Google Earth. Each ship icon represents most recent post from either a live expedition or one within last 6 months (look for yellow-filled ship icon) or post from beginning of a historical expedition (look for blue-filled ship icon). Open this kml in Google Earth and discover for yourself.
Google posted two tutorials on Geospatial Data Abstraction Library (GDAL): “Converting GIS Vector Data to KML walks through the basics of converting GIS vector data to KML using the OGR open source library. And Creating super-overlays with gdal2tiles walks through the basics of creating a super-overlay, a set of ground overlays that use region-based NetworkLinks, using the open source gdal2tiles utility.”