Many believe mat oft-told legends refer to this event, and would place it at about 33,000 years before the present. But geological data suggest mat the event occurred at least 200,000 years ago. The two remaining moons cause major changes in Arrakis's rotation about ks own axis. The Twins also contribute, but their effects are long-term. Arrakis averages 22.4 standard hours per day. However, the shortest days of record occurred from J2310 to 12420 with the absolute shortest day being 5.28 hours in duration. This occurred on 5 nl-roodim 12370 Imperial. The longest day recorded thus far was 43.2 standard hours (25 nAtaaaim 15052 Imperial). Theoretical calculations show mat under special circumstances the day can be as short as 3.81572 hours and as long as 51.36405 hours. These changes in rotation rate, as well as the effects of Menaris and Extaris have had profound impact on the geologic evolution of Arrakis. MORPHOLOGY. The first complete mapping and interpretation of the surface of Arrakis was done by Kyncs (10901), who claimed to be an eighth generation descendant of the famous planetotogist of the same name who lived during the time of Paul Maud'Dib. Dramatic changes have occurred since then and these changes as well as present topography are detailed by Xcnach (15029). At present many mountain ranges and deep valleys (grabens) exist in all regions of the planet, a situation similar to that of the earliest known phase of me planet's history. During the middle phase, as existed during tones's time, extensive desertification had occurred. The earlier mountains had been severely eroded, primarily by sand blasting, and the surface was mostly flat except for isolated garres and ridges, a few volcanic peaks such as Mt, Idaho, Mt. Kynes, and Observatory Mt., and the dune fields. It is only because the planet is so geologically active that any elevation difference, other than the sand dunes, existed at all during the middle phase. Arrakis is the most geologically active of all Neta planets and the rate of mountain building almost managed to keep pace with rapid erosion by sand blasting. Today with much-reduced eolian erosion as a result of the greening of Arrakis, and with little in the waj of water erosion, mountains are rising rapidly (rapidly m a geological time sense). Mt. Idaho is still the highest peak. Its summit is currently 9,524 meters above the bled, compared to only 7,393 meters seven thousand years ago. Several mountain ranges now have peaks exceeding 7,400 meters in elevation. There are numerous deep valleys (grabens), the greatest nf which is Grose Valen, with maximum depth of 1,250 meters, maximum width of 2,800 meters and a length of about 730 km. During the desertification phase of the planet's history, most of these were filled with dust and called tidal dust basins or dust chasms by the natives. Today many of these chasms have re-opened through geological processes, and many more have formed. The major grabens are not formed by running water; rather they are a result of the dynamic development of the planet, discussed in the next section.