Plate Tectonics and Landforms

Plate tectonics describes plate motion and the effects of the motion Plate tectonics describes plate motion and the effects of the motion. Plate tectonics says that Earth’s outer shell is made of about 20 plates. The plates are rigid and in constant motion relative to one another.

The largest plates consist of two different kinds of crust; oceanic and continental. Many of the smaller plates contain only oceanic crust.

Continental crust is thicker and less dense than oceanic crust Continental crust is thicker and less dense than oceanic crust. Continental crust is composed mostly of the igneous rock granite, while ocean crust is mostly the igneous rock basalt.

The plates sit on the hot asthenosphere The plates sit on the hot asthenosphere. While the rock in the asthenosphere is solid, it is less rigid than the plates, and therefore moves. The movement within the asthenosphere is caused by heat from the core of the earth.

https://youtu.be/ryrXAGY1dmE The heat rises slowly through the earth creating convection cells within the asthenopsphere. https://youtu.be/ryrXAGY1dmE The material carried by convection cells in the asthenosphere drag the plates along.

By destroying and creating plate material, plate tectonics constantly recycles Earth’s materials.

Each plate moves as a distinct unit Each plate moves as a distinct unit. The borders between plates are called plate boundaries.

The interaction between plates results in different effects on the earth’s surface. One of the effects of plate motion is the Ring of Fire. The Ring of Fire is an area of volcanoes that form a ring around the Pacific Plate.

Convergent– plates move toward one another Ocean / Continental Continental / Continental

https://youtu.be/NbDqJy28hBw Oceanic/Continental: plates are colliding and ocean crust is subducted, or pulled into the mantle, and melted. This process forms deep ocean trenches and destroys plate material in what we call the subduction zone. Harry Hess predicted that this was happening. https://youtu.be/NbDqJy28hBw

Tight lines of volcanoes create island and volcanic arcs Landforms: Deep Ocean Trenches Tight lines of volcanoes create island and volcanic arcs Places: Cascade Mountain Range, Oregon and Washington, Mt. St Helen Mariana Trench

Continental / Continental Crust Plates crash into one another No volcanic activity Landforms Mountain Ranges Places Himalaya Mountains, India https://youtu.be/loFxYSHxTf0

Divergent - plates move away from one another (seafloor spreading) New crust material is created Shallow earthquakes along the plate boundary Ocean/ocean crust

Landforms Creates Mid-ocean Ridge Rift Valleys Places Mid-Atlantic Ridge, Atlantic Ocean

Transform—plates grind past one another Shallow Earthquakes Some volcanoes, but spread out Mostly Ocean Crust Some Continental

Landforms Faults (breaks in rock) Places San Andreas Fault, California

Plate Tectonic Lab next week