How Do Tectonic Plates Work?

How Do

TECTONIC PLATES Work?

Plate Theor Alfred Wegener was born on November 1st 1880 and was the first scientist to come up with the tectonic plates theory. Below are some extractions from his diary as he was coming up with the theory:

17th June 1901 Today as I was looking at a map I noticed something. Some of the continents on the map looked like they would fit together - almost like a jigsaw! The most prominent example of this was the border of South America and the border of Africa. I wonder what this could mean.

6th August 1901 I keep thinking about the continents fitting together like a jigsaw. It is possible that the earth’s continents were once all joined together but that they gradually moved apart over millions of years. This theory also explains some other mysteries such as why similar fossil and rock formations can be found on different continents. Some scientists guess that there used to be ‘land bridges’ that would allow animals to move freely between different continents but I have always been skeptical of this theory.

13th January 1902 Everyone knows that mountains are formed when the earth cools down and contracts - or do they? If this is the case, why are mountains not spread evenly across the earth’s surface? On the other hand, if the earth was made up of moving plates, mountains could be formed when 2 plates made contact with each other. I believe that the Himalayas were formed by India coming into contact with Asia. Plates moving past and bumping into each other would also explain why earthquakes and volcanos always seem to happen in the same places.

ry

23rd March 1902 The other scientists would laugh me out of a job if I said any of this to them. I’m just going to focus on meteorology, that’s where my heart lies. My main focus should be getting a place on the 1912 Greenland expedition.

6th January 1912 My place on the Greenland expedition is secured and I couldn’t keep quiet about my theory any longer. It just makes so much sense. I presented my hypothesis today in front of a whole crowd of other scientists.

At least I was right about their reaction. But I know I have discovered something. They told me to focus on meteorology, and I will – for now.

16th May 1915 I’ve done it! I’ve published a book. I’ve gathered all of the evidence that points towards there having been a singular massive continent which I call ‘Urkontinent’. Hopefully this book will allow the other scientists to see where I am coming from.

September 4th 1920 I am writing this from my Greenland tent. While we were out earlier measuring ice thickness we made an amazing discovery! Shallower oceans are geologically younger than deeper oceans. This again points to my theory being correct. I can’t wait to arrive back in Berlin and dig more into it.

FOOTNOTE Unfortunately Alfred Wegener never made it home from his final expedition, instead passing away in Greenland. However, his theory managed to live on. It was still disregarded by scientists until the early 1950’s when finally it was studied more at the University of Cambridge and proven to be correct.

Earth Layers Lithosphe

re Crust

Mantle Asthenosp he

re

Outer Core Inner Core

d i u q i L Solid

3rd October 1905 The top layer of the earth is called the Lithosphere, which I believe is completely made up of tectonic plates.

There are oceanic plates and continental plates. Oceanic plates are much denser than continental plates. Oceanic plates are found at destructive plate boundaries as they subduct continental plates on impact. Some plates however can be both continental and oceanic. Mountains are created when 2 continental plates crash into each other.

MOVEMENT Tectonic plates move because they are sat upon the mantle of the earth which is made up of magma. This magma moves in a convection cell which is created when the magma when gets really hot and rises then cools and begins to sink back down.

Plate movements can now be tracked using GPS technology.

Mantle Convection Cell

Convection Cell

Outer Core Inner Core

Plate Mo At a convergent boundary, a denser plate made of oceanic crust is subducted under a less dense plate made of either continental or oceanic crust. Earthquakes and volcanos are common near convergant boundaries.

Mountain Range t

Continental Crus Continental Crust

Lithosphere

Lithosphere

Asthenosphere

Asthenosphere

Convergent Boundary

A divergent boundary is a linear feature that consists of 2 tectonic plates moving away from each other.

Most divergent boundaries are formed between 2 oceanic plates. Divergent boundaries can form volcanic island ranges.

Ocean Oceanic Crust

Lithosphere

Magma

Divergent Boundary

ovement Continenta l Lithosphe

re

Asthenosp he

re

Crust

Continenta l

Crust

Lithosphe

re

Asthenosp he

re

Transform Boundary

17th July 1913 Plates moving together in this way explains why earthquakes and volcanos always occur in the same places.

It could also mean that the sea’s floor is constantly expanding.

A transform boundary neither creates nor destroys. Most transform boundaries are hidden in deep oceans, and assist with sea floor spreading.

The most well known transform boundaries however are on the edges of tectonic plates and can create earthquakes due to friction.

Plate Bound

daries & Names

Continen

Permian

ยง

225 Million Years Ago

ยง

Jurassic 150 Million Years Ago

Triassic 200 Million Years Ago

ยง

Cretaceous 65 Million Years Ago

P

ntal Drift

n §

Present Day

Continental drift is all about how the earth’s continents move in relation to each other, appearing to drift across the ocean. In the Permian era, the earth’s continents were all joined together in what Wegener referred to as ‘Urkontinent’.

Today however, we call it Pangea. In the Triassic era, the 2 separate continents were known as Laurasia and Gondwanaland.

The continents kept drifting apart over time until they reached the formation that they exist in now.

17th June 1918 Seafloor Spreading is all about new crust being formed on the floor of the ocean. This new crust is formed when 2 oceanic ridge plates move away from each other and the magma underneath rises up. When this magma reaches the surface, it cools suddenly forming the new rock.

The fossils below are all examples of the fossils that made Wegener begin to develop his ideas of Seafloor Spreading, Continental Drift & Tectonic Plates.

Cynognathus

Mesosaurus

Glossopteris

Lystrosaurus

Seafloor Spreading further e b l il w s k c o r the older e s u of a c n e t b e t t is a p e n o e z h t g in w oor spread ed to follo e fl n a e s t s e ju h t u o e Y r e r. h e ill be clos w s You can tell w k c o r r e g n u d the yo n a t i g zone. in m o d a fr e r y p a s e aw h t d will fin u o y d g away n a in v s o k c m o r s e t la p oy unger d the 2 n a d e r u t c a year. a fr m g c in 10 v a f h o e d r e e e h p p s s ove at a s the litho m s w e o t h s la p w e lo h e T b . to rise up a The diagra m v la e h t w o ll r that a from eac h othe

Ocean

Oceanic Crust

Lithosphere

Magma

Affected San Francisco is an area prone to earthquakes. This is because it is situated along the San Andreas faultline where the Pacific plate and the North American plate move alongside each other.

Mount Everest is part of the Himalayas in Nepal. The Himalayas were formed when the Indian tectonic plate converged with the Eurasian tectonic plate.

Naples is home to the only active volcano in Europe - Mount Vesuvius.

Mount Vesuvius was created at a connvergent boundary.

d Places

Volcano Crust Magma/Lava

This is a drawing of the last photo ever taken of Alfred Wegener before his untimely death in 1920

This publication was put together by Emily Whiteford & Jenni Walker