Here are some of the twitter feeds to follow if one are interested in Earth Science subjects such as earthquakes, tsunami, plate tectonics, geodesy, etc.
Organizations
Follow @theAGU
Tweets by American Geophysical Union
Follow @astQuake
Tweets by EMSC
Follow @CATnewsDE
Tweets by CATnewsDE
Follow @IRIS_EPO
Tweets by IRIS
Follow @geoscope_ipgp
Tweets by IPGP Geoscope
Individuals
Follow @stef92320
Tweets by Dr. Stéphane Baize
Follow @earthquakeguy
Tweets by Dr. John Cassidy
Follow @TTremblingEarth
Tweets by Dr. Austin Eliot
Follow @seismo_steve
Tweets by Dr. Stephen Hicks
Follow @SeismoSue
Tweets by Dr. Susan Hough
Follow @eruptionsblog
Tweets by Erik Klemetti
Follow @RLacassin
Tweets by Dr. Robin Lacassin
Follow @ALomaxNet
Tweets by Dr. Anthony Lomax
Follow @CPPGeophysics
Tweets by Dr. Jascha Polet
Follow @SinistralSeismo
Tweets by Dr. John Ristau
Follow @DepressedDarth
Tweets by Darth Vader
Follow @SotisValkan
Tweets by Sotiris Valkaniotis
National Park Tweets