These boundaries are thought to form between the core and the mantle due to the temperature instabilities that occur at these boundaries

The two plates move away in opposite directions and in between fills with molten rock from below creating new sea floor

This process as it continues forms chains of volcanoes and rift valleys called mid-ocean ridge or spreading ridge

The rate that this spreading occirs varies from 2.2 inches to 12.6 inches a year depending on the ridge

Did you know that the longest mountain range is caused by this sea-floor spreading?

It is 47,000 miles long and is underwater

1. When do divergent plate boundaries occur? When the plates move apart in opposite directions and in between fills with molten rock When the plates slide under each other 2. What is a chain of volcanoes and rift valleys called? Mid-ocean ridge Sea floor spreading 3. What do experts think causes the plates to move? The different types of sea currents that occur at the boundaries The temperature instabilities at the boundaries 4. How fast do plates spread apart? 2.2-12.6 inches per year 5-20 feet per year

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