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| Question | Answer |
| What is Seafloor Spreading? | It is when continents are being pushed apart. |
| Who is Harry Hess? | He is a geologist and U.S. Navy Reserve Rear Admiral |
| What did he propose? | He proposed that the seafloor itself was pushing the continents apart. |
| What does SONAR stand for? | Sound Navigation and Ranging |
| What does it do? | It is helpful for exploring and mapping the Ocean because sound waves travel farther in the water. Also, it emits an acoustic signal or pulse of sound into water. |
| What is Mid-Atlantic Ridge? | It is an oceanic ridge found along the Atlantic Ocean Floor. It is a 12,000 mile long mountain range. |
| What did Hess discover? | He discovered that the age of the Atlantic Ocean Floor was progressively older the further it moved away from ridge. The ridge he thought was where new seafloor was being added to the Earth's lithosphere which pushed the continents apart. |
| What is the Hess Theory? | It is a theory which explains that the Mid-Atlantic Ridge was a boundary where two lithospheric plates were rifting. As that happened, rising magma from the upper mantle filled the cracks and created new crust. |
| What does magma solidify to? | Basalt and Igneous Rock |
| What does a Conveyor Belt do? | It continually adds seafloor, very slowly over time, widening the Atlantic Ocean basin and pushing the continents to either side. |
| What did Hess suggest? | If oceanic ridges were expanding along the Earth's crust, then it must be shrinking somewhere else. |
| What explained this? | Oceanic crust eventually descends into oceanic trenches--very deep narrow canyons along the rim of the pacific ocean basin. (the Atlantic Ocean was expanding and the Pacific Ocean was shrinking) |
| What happens when old oceanic crust get consumed in trenches? | New magma rises and is erupted along the spreading ridges to form new crust. |
| What became the effect of this? | Ocean basins were being recycled with the creation of new crust and destruction of the old oceanic lithosphere simultaneously. |
| Who coined the term "Seafloor Spreading?" | Robert S. Dietz |
| What evidences supported The Hess Theory? | 1. At/near the crest of the ridge, the rocks are very young and they became progressively older away from the ridge crest |
| What evidences supported The Hess Theory? | 2. The youngest rocks at the ridge crest always have present-day or normal polarity. |
| What evidences supported The Hess Theory? | 3. Strips of rock parallel to the ridge crest alternated in magnetic polarity suggesting that the Earth's magnetic field has flip-flopped many times. |
| What is the natural tape-recording of the history of the reversals in the Earth's magnetic field? | Oceanic Crust |
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