1. Mid-Ocean Ridges 1. Mid-Ocean Ridges How Do We Know? We know - - PowerPoint PPT Presentation

Modern Theory of 
 Plate Tectonics

Modern Theory

• The Modern Theory of Plate Tectonics

is built on Alfred Wegener’s theory of Continental Drift.

• Two new discoveries (discoveries over

the last 60 years) helped scientists develop the modern theory of Plate Tectonics.

• 1. Mid-Ocean Ridges
• 1. Mid-Ocean Ridges
• What is it?
• A large mountain range at the

bottom of an ocean.

• 1. Mid-Ocean Ridges
• How Do We Know?
• We know about Mid-Ocean

Ridges because of Marie Tharp and her analysis of sea-floor data! She first detected the ridge in 1952.

Marie Tharp

Marie Tharp’s Map

Mid-Atlantic Ridge

Sonar imaging was the technology used to discover the Mid-Atlantic Ridge.

Mid-Atlantic Ridge

Discover more about Sonar Mapping by visiting this website. Write a summary

• f how sonar is used to map the seafloor

https://goo.gl/YuyH5C

Mid-Atlantic Ridge

Mid-Atlantic Ridge

Iceland sits on the Mid- Atlantic Ridge. The magma from the ridge, combined with a hot spot beneath the island, pushed the land above the ocean’s surface.

Mid-Atlantic Ridge

Describe the movement of magma under a Mid-Ocean ridge.

Mantle Mid-Ocean Ridge

Ocean Floor

• 2. Ocean Trenches

• 2. Oceanic Trenches

The location where the Earth’s crust is pulled back into the mantle (subduction zone)

The North American Plate is being pulled under the Caribbean Plate Caribbean Plate The North American Plate Deepest place

• n Earth

Mantle Mid-Ocean Ridge

Ocean Floor

Trench Trench

Stop and Check

Where is the mid-ocean ridge?

Stop and Check

Where are the oceanic trenches?

Stop and Check

At which location is the temperature highest?

A B C D

The End Matching

Youngest Crust Ridge

Matching

Oldest Crust Trench

Matching

Coldest Trench

Matching

Warmest Ridge

Matching

Thinnest Ridge

Matching

Thickest Trench

The End Stop and Check

At which point is the crust the most thick?

A B C D