Transcript Restless Continents

• Theory that all of the
continents were once one
large landmass (Pangaea) that
has broken up and drifted
apart.
– Alfred Wegener
• Evidence
– Continents fit like pieces of a
puzzle
– Fossils of same species
animal & plants found on
separate continents
• Glossopteris
– Rock formations
• Matching mountain chains
– Climatic conditions
• Coal fields in Antarctica
• Pangaea
– Greek for “ all Earth”
• Pangaea broke into two huge continents
– Laurasia
– Gondwana
• These two split again to form the current continents
• Mid-ocean Ridges
– Underwater mountain chain
that runs through the
Earth’s oceans.
• Sea-floor spreading
– Process in which new
lithosphere forms
• Magma rises to the surface
through the mid-ocean
ridge forming new oceanic
crust
• Tectonic plates spread
apart and magma fills the
gap.
• As new crust forms older
crust moves away from the
M.O.R.
• Crust closer to the
mid-ocean ridges is
younger than crust
further away.
• Subduction
– Process in which old
ocean floor goes back
into the mantle
through trenches
• Earth’s north and south
poles have changed
places many times
• Molten rock contains
contains tiny grains of
magnetic minerals
• These minerals align with
the magnetic field of the
Earth.
• As the magnetic field
reverses and the ocean
and new ocean floor is
formed it leaves a record
of this change.