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The
map is designed to show Earth's most prominent features when viewed from
a distance, and more detailed features upon closer inspection. The back
of the map zooms in further, highlighting examples of fundamental processes,
while providing text, timelines, references, and other resources to enhance
understanding of this dynamic planet. The main and polar maps, above,
are interactive, inviting you to make your own regional map, using whichever
"layers" you choose. Data for any volcano, earthquake, or impact symbol
can be found via the "Identify" tool. |
Most
new crust forms at ocean ridge crests, is carried slowly away by plate
movement, and is ultimately recycled deep into the earth—causing earthquakes
and volcanism along the boundaries between moving tectonic plates. Oceans
are continually opening (e.g., Red Sea, Atlantic) or closing (e.g., Mediterranean).
Because continental crust is thicker and less dense than thinner, younger
oceanic crust, most does not sink deep enough to be recycled, and remains
largely preserved on land. Consequently, most continental bedrock is far
older than the oldest oceanic bedrock (see back of map).
The earthquakes and volcanoes that mark plate
boundaries are clearly shown on this map, as are craters made by impacts
of extraterrestrial objects that punctuate Earth's history, some causing
catastrophic ecological changes. Over geologic time, continuing plate
movements, together with relentless erosion and redeposition of material,
mask or obliterate traces of earlier plate-tectonic or impact processes,
making the older chapters of Earth's 4,500-million-year history increasingly
difficult to read. The recent activity shown on this map provides only
a present-day snapshot of Earth's long history, helping to illustrate
how its present surface came to be.
Both the front and back of this map illustrate
the enormous recent growth in our knowledge of planet Earth. Yet, much
remains unknown, particularly about the processes operating below the
ever-shifting plates and the detailed geological history during all but
the most recent stage of Earth's development. |