Plate Tectonics the movement of Earth Tectonic Plates

Plate Tectonics the movement of Earth

Tectonic Plates • Earth’s lithosphere is broken into about 19 pieces • These plates move on top of the asthenosphere

Plate Boundaries • Places where the plates meet

Types of Plate Boundaries • Transform Fault Boundaries –(Sliding) • Divergent – Moving apart / Rifting • Convergent – Colliding / Sub-duction

Transform Fault Boundaries • Faults form when plates slide past each other • A fault is a large crack in rocks that can break • EARTHQUAKES can happen along fault lines

San Andreas Fault, CA

Divergent Boundaries • Boundary between two plates that are moving apart or rifting • RIFTING causes SEAFLOOR SPREADING

Divergent Plate Movement: Seafloor Spreading • the movement of two oceanic plates away from each other (at a divergent plate boundary), which results in the formation of new oceanic crust (from magma that comes from within the Earth's mantle) along a mid-ocean ridge. • Ocean floor spreading was first suggested by Harry Hess and Robert Dietz in the 1960's.

Features of Divergent Boundaries • Mid-ocean ridges

Features of Divergent Boundaries • Rift valleys Quilotoa, Ecuador

Features of Divergent Boundaries • Fissure volcanoes Hawaii, USA

Convergent Boundaries • Boundaries between two plates that are colliding • Different things can happen, depending on the density of the plates involved. • There are 3 types…

Oceanic-Continental • Ocean plate colliding with a less dense continental plate • Subduction Zone: where the less dense plate slides under the more dense plate • VOLCANOES occur at subduction zones

Andes Mountains, South America

Oceanic-Oceanic • Ocean plate colliding with another ocean plate • The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH

• Two Oceanic Plates - When two oceanic plates collide, one may be pushed under the other and magma from the mantle rises, forming volcanoes in the vicinity

Aleutian Islands, Alaska

Continental-Continental • A continental plate colliding with another continental plate • Have Collision Zones: –a place where folded and thrust faulted mountains form.

• Two Continental Plates - When two continental plates collide, mountain ranges are created as the colliding crust is compressed and pushed upwards.

Fold: When rocks bend • Anticline (Upward) • Syncline (Downward)

Causes of Plate Tectonics

Convection Currents • Hot magma in the Earth moves toward the surface, cools, then sinks again. • This circulation of heat creates convection currents. • Convection currents beneath the plates cause the plates to move.