Subduction Zones

Geosyncline

What We Actually See

What Does This Look Like?

Andes – True Scale

Continent-Continent Collision

Continent-Terrane Collision

Where Does Ocean Crust Go? Hugo Benioff, 1954

1. How we know plate tectonics happens

Benioff’s Interpretation

1. How we know plate tectonics happens

Benioff’s Interpretation Updated

1. How we know plate tectonics happens

How Plates Move

A Subduction Zone

Subduction and Metamorphism

Why Mountains are High

Where the Plates Meet

Terrane Accretion

Terranes in Western North

America

Subduction Zone Rocks

Steinmann Trinity (1905)

• Serpentinite• Pillow Basalt• Radiolarian Cherts

• Characteristic of ophiolite settings• Other Distinctive Rocks– Graywacke and Flysch– Blueschist

Bedded Chert

Serpentinite

Serpentinite

Magnesite Mines in Serpentinite

Pillow Lava

Pillow Lava

Pillow Lava

Blueschist

Graywacke

Flysch

Melange

Melange

Eclogite

Molasse, Switzerland

Molasse and the High Alps

Wisconsin 2 Billion Years Ago

1900 MY Penokean Orogeny

Before the Penokean Orogeny

First Collision

Second Phase

Marshfield Terrane Collides

Assembling North

America

Assembling North

America

1700 MY Granite and Rhyolite

Mazatzal Orogeny

Cactus Rock

Baraboo Interval Quartzites

“Baraboo Interval”

Yavapai Orogeny

Baraboo Quartzite

Mazatzal-Yavapai Events

1450 MY Wolf River Batholith

Wolf River Batholith

1100 MY Mid-Continent Rift

The Grenville Orogeny Begins

The Grenville Orogeny

A Subduction Zone

How Arcs Grow

Exotic Terranes