William Treurniet at http://www.treurniet.ca/MayanCal/ has made a fascinating analysis showing a link between the onset of the Galactic Underworld and the frequency of earthquakes in the lower mantle.
The data base providing for this statistical analysis is very large and so
this would point to a link between vibrations close to the 13 Hz level of the inner spherical structure of the earth and the activation of said Underworld. Hence, consciousness changes may be related to the earth's seismic activity.
While the link between an intensified seismic activity as a result of the the onset of the Galactic Underworld in 1999 (and its preceding thirteen-tun period in 1986) seems undisputable I would personally consider the link to its Day/Night structure as suggestive rather than conclusive. To my knowledge Treurniet's study represents the first solid empirical study showing a link between earthquake activity and the Mayan calendar.
Food for thought you may enjoy!

Carl Johan Calleman
cjcalleman@swipnet.se