There are a few people that have impacted the history in regards to how we began to know about the tectonic plates. The first being Alfred Wegener, the second being Marie Tharp, and the third being Harry Hess.

Alfred Wegener was a meteorologist that noticed that the continents fit together and there are relationships between where the fossils are on the continents and where he believes the continents would fit back together, because of this, Wegener came up with a theory about continental drift, but it was not believed because he had no mechanism.

Marie Tharp was an oceanographer in the 1960's, she helped develop the first map of the ocean floor by being at a base while a crew was on a boat with a sonar machine. This sonar machine was originally used in World War II to detect u-boats by sending sound waves through the water and timing how long it took for the wave to come back to the boat.

Then we have Harry Hess, which came up with the idea of convention currents in the 1970's. Harry Hess also took the idea of continental drift and changed its name to be plate tectonics.

I want to discuss how plate tectonics affect earthquakes. To begin, we need a basic knowledge of tectonic plates. These are plates that are constantly moving. Plates meet and move at what we call "boundaries." There are three types of boundaries:

convergent: one plate moves toward (sometimes beneath) another

Divergent: plates move outward from one another

Transform: the plates slide against one another

We feel earthquakes in waves. There are a few different types of waves being:

Primary (P-waves): Compressional waves

secondary (S-waves): longitudinal waves

Primary waves are compressional waves, these compressional waves are faster moving than the S-waves. When I think about P-waves, I visualize a slinky being stretched out at both ends and pulling a few rings towards one end and then releasing them and seeing what it does, this is how P-waves act. Then we have secondary waves, secondary waves are longitudinal waves. Longitudinal waves move up and down like a sine wave. The last photo to the left shows how primary and secondary waves act within the surface of the ground.

earthquakes occur when there is stress placed on the boundary. Earthquakes happen in a plane called the rupture surface, it does not happen all at once, but starts at the hypocenter which is beneath the surface of the ground and an epicenter that is on the surface. When stress is placed on the boundary it then is released in what we feel and call an earthquake, the stress that was within the boundary is then displaced elsewhere along the rupture surface.

I have experienced quite a few earthquakes. A few years back on fourth of July in 2019, was the last major earthquake I felt. It was very interesting to experience because I was relaxing in bed when it happened and the blinds started shaking and the ceiling fan above me was rocking and at first I was confused what was happening and then it clicked and I was like "oh this is an earthquake." This earthquake felt like it rolled through.

Works Cited

Cooper, Jamey. “Earthquake Lecture" 20 September 2022.

“Alfred Wegener .” Study.com, https://study.com/learn/lesson/alfred-wegener.html.

Fecht, Sarah. “8 Surprising Facts about Marie Tharp, Mapmaker Extraordinaire.” State of the Planet, 31 July 2020, https://news.climate.columbia.edu/2020/07/29/surprising-facts-marie-tharp/.

Harry Hess - Hydrothermal Vents. https://sites.google.com/site/vanhervey/theories-of-plate-tectonics/harry-hess.