During the Silurian, Earth underwent
considerable changes that had important repercussions for the environment
and life within it. Plate tectonic activity continued to shift the
continents during the Silurian. The great southern continent of
Gondwana drifted farther across the South Pole,
while Siberia, Laurentia and Baltica clustered around
the equator. Laurentia and
collided at the end of the Silurian, forming a new supercontinent,
Euramerica, and raising new mountain ranges. Rising sea level formed
a nearly continuous sea from New York to Nevada, and other shallow
seas still covered parts of other continents.
The Early Silurian was also a time of global icehouse
climate that included great ice sheets at high latitudes. By
the middle of the Silurian, however, global climate had become much
warmer, comparable to that of most of the Ordovician
and Devonian Periods. A new greenhouse
phase began, leading to the melting of many large glacial ice
sheets, which contributed to a substantial rise in global sea level.
The result was a world with distinct north-south climatic zones,
much as today. Glaciers remained at high latitudes, but lower latitudes
were relatively warm and arid conditions led to the formation of
extensive evaporite (salt) deposits near the equator.