Do First Actions Turn in yesterdays lab Questions
Do First Actions: Turn in yesterday’s lab Questions: 1. Why does an oceanic plate slide under a continental plate when they converge? 2. What is the above process called?
Agenda 1. Plate Interaction Notes 2. Why Plates Move the Way they Do Video Review
What are Plates? • Lithosphere is broken in parts called plates. • The Earth’s crust and upper mantle=lithosphere
Types of Plates • Oceanic plates - plates below the oceans • Continental plates - plates below the continents Which type of plate is more dense?
Plate Tectonics • Plate tectonics refers to the movement of plates on top of the asthenosphere (putty layer), which is a part of the mantle. • There are 12 plates moving in various directions very slowly (2 -5 cm a year) • The interactions of these plates create structures or “tectonic features”
Plate Tectonics
Why Plates Move 1. Convection Currents • Hot magma in the Earth moves toward the surface, cools, then sinks again • Causes the asthenosphere to move which forces the plates on top of them to move like an object on a treadmill • The individual currents are known as convection cells 2. Gravity • Pushes down on the plates • Forces the denser plates to sink
Why Plates Move tinyurl. com/k 8 jaj 7 p
Plate Boundaries • Plate boundaries are where plates touch • There are three types of movements at plate boundaries: 1. Divergent 2. Convergent 3. Transform ↑↓
Three Basic Types of Plate Boundaries Divergent Using hands to show relative motion Transform Convergent USGS Graphics
Divergent Boundaries What’s happening? • Boundary between two plates that are moving apart or rifting • RIFTING causes SEAFLOOR SPREADING What features are formed? • Mid-ocean ridges (ocean) • rift valleys (continent) • fissure volcanoes
East African Rift Valley
Convergent Boundaries What’s happening? • Boundaries between two plates that are colliding • There are three types: 1. Oceanic – Continental 2. Oceanic – Oceanic 3. Continental - Continental
Type 1: Oceanic - Continental What’s happening? • Oceanic plate colliding with a less dense continental plate What features are formed? • Subduction Zone: where the denser plate slides under the less dense plate forming a trench • Where plates are recycled into the mantle • VOLCANOES occur at subduction zones
Andes Mountains, South America
Type 2: Oceanic - Oceanic What’s happening? • Oceanic plate colliding with another oceanic plate What features are formed? • Subduction Zone or Trench • Volcanos
Aleutian Islands, Alaska
Type 3: Continental – Continental What’s happening? • A continental plate colliding with another continental plate What features are formed? • Mountains
Transform Fault Boundaries What’s happening? • Boundary between two plates that are sliding past each other What features are formed? • Earthquakes
San Andreas Fault, CA
Three Basic Types of Plate Boundaries Divergent Transform Convergent USGS Graphics
Video • Watch the short video to understand why and how plates move http: //tinyurl. com/l 2 mnmue or
DYL 1. What are the 3 types of plate interactions? 2. What type of interaction is shown in the picture below?
Resources • http: //pnsn. org/outreach/about-earthquakes/plate-tectonics • http: //www. planetseed. com/files/flash/science/features/earth/living planet/plate_boundaries/en/index 3. html? width=570&height=475&p opup=true
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