DO NOW

1. What is the Geologic Time Scale based on?2. What 2 events characterize the Cenozoic Era?3. What 2 events characterize the Quaternary

Period?4. What are the two types of crust and how are

they different?5. Describe the consistency of the upper

portions of Earth’s mantle

Unit 1- Earth Systems and Resources

Plate Tectonics

AIM: What are tectonic plates and how have they moved over time?

Lithosphere

• The solid, outer part of Earth• Consists of the crust, and the uppermost

mantle

Asthenosphere• Upper portion of the mantle that has a

“plastic-like” consistency

Asthenosphere – “plastic like”

Lithosphere – Solid

• Earth’s lithosphere is divided into several large pieces called “tectonic plates”

• The plates are constantly moving, a phenomena known as “plate tectonics”– 2-5 cm a year

• The plates (lithosphere) are able to glide on the plastic-like portion of the mantle, known as the asthenosphere

• The lithosphere glides on the asthenosphere

• Slow creeping motion of the mantle is caused by convection currents, carrying heat from Earth’s interior to the surface

Convection currents in the asthenosphere move plates in the lithosphere

Theory of Plate Tectonics..

• The theory of plate tectonics arose out of 2 separation geological observations:– The continental drift theory– The seafloor spreading theory

Continental Drift• Alfred Wegner proposed that all present-day

continents originally form one land-mass- Pangaea

• Wegner proposed that this supercontinent began to break up 200 million years ago

1. Fossilized tropical plants were found in Greendland’s icecaps

2. Tropical regions on some continents had polar climates in the past

3. The continents fit together like puzzle pieces4. Similarities existed in rocks between the east coast

of North and South America and the west coasts of Africa and Europe

5. Fossils of extinct land animals were found on separated land masses

• Tropical plants fossils in cold climates• Continents fit like a puzzle• Coasts of different continents have same rocks• Fossils of extinct species found on separated

landmasses

Plate Tectonics

• Earth’s lithosphere is divided into 8 major plates • Divisions between plates are called boundaries

Plates interact at their boundaries

• There are 3 types of plate boundaries– Transform boundaries– Divergent boundaries– Convergent boundaries

Transform Boundaries• Two plates slide past each other

Divergent Boundaries

• Two plates slide apart from each other

Convergent Boundaries

• Two plates slide towards each other• If an oceanic plate and a continental plate are

colliding, the oceanic plate will slide under the continental plate– The oceanic plate is more dense– This is called SUBDUCTION