Plate Tectonics

Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell - huge, thick plates that drift atop the soft mantle.

The Crust Outermost layer 5 – 100 km thick Made of Oxygen, Silicon, Aluminum

The Mantle Layer between the crust and core Contains most of the Earth’s mass Is denser than the crust

The Core Below the mantle and to the center of the Earth Believed to be mostly Iron

Tectonic Plates

Plate Tectonics Greek – “tektonikos” means builder Pieces of the crust/upper mantle that move around Each plate has a name Fit together like jigsaw puzzles Float on top of mantle similar to ice cubes in a bowl of water

Continental Drift Alfred Wegener 1900’s Continents were once a single land mass that drifted apart. Similar fossils were found on different continents. Called this supercontinent Pangea, Greek for “all Earth” 245 Million years ago

Evidence of Pangea

Volcanism is mostly focused at plate margins Pacific Ring of Fire

Ring of Fire The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes The Ring of Fire is a direct result of plate tectonics and the movement and collisions of techtonic plates

What is a volcano? Mountain or hill – Has crater or vent in the top – Gases/Magma can escape through this vent Size of Volcano includes material that flows down the die vent cone magma chamber conduit

Types of Volcanoes An active volcano is a volcano that has had at least one eruption during the past 10,000 years. An erupting volcano is an active volcano that is having an eruption... A dormant volcano is an active volcano that is not erupting, but supposed to erupt again. An extinct volcano has not had an eruption for at least 10,000 years. Not expected to erupt again.

Lava Types Large amounts of gas and a high viscosity (sticky) magma create an explosive eruption! – Called pyroclastic eruptions Small amounts of gas trapped magma will form a runny eruption. – Called effusive eruptions

Sticky Magma = explosive/pyroclastic eruptions What can happen? - Ash fall Super heated rock and ash falling from the sky – Pyroclastic flow Lava flows; moving liquid rock, ash and gas. Explosive Eruptions

Pyroclastic Flow - direct impact Courtesy of

Pyroclastic Flow - burial

Pyroclastic Flow - burns

From above you can see their fine grainsize and the distinctive slight ridges and grooves that show which way the mass of hot dusty air was moving.

Effusive Eruptions Runny lava eruption. – Called effusive eruptions Effusive eruptions have fast moving lava on to the ground. Hawaii Courtesy of

Sea Floor Spreading

Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins Magma rises to the surface and solidifies and new crust forms Older Crust is pushed farther away from the ridge -Soil at the Mid-Atlantic Ridge is “younger” than soil in locations further from the ridge

How Plates Move

Different Types of Boundaries

Divergent Boundary – Arabian and African Plates

Divergent Boundary – Iceland

Divergent Boundary - Oceanic

Divergent Boundary - Continental

Convergent Boundary – Indian and Eurasian Plates

Convergent Boundary – Oceanic & Continental &

Convergent Boundary – Oceanic & Oceanic &

Convergent Boundaries - Continental &

Transform Boundary – San Andreas Fault

Review Name the 3 main layers of the Earth What is a tectonic plate? What was Pangea? What is Sea-Floor spreading? Name the three different types of plate boundaries and one location on Earth for each one