# Breaking up of continents- Plate movement... **URL:** \ **Category:** Factual Questions\ **Created:** [July 31, 2002, 8:12am UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663 "2002-07-31T08:12:25Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Aro](https://avatars.discourse-cdn.com/v4/letter/a/b3f665/32.png) [@Aro](https://boards.straightdope.com/u/Aro)\ **Post date:** [July 31, 2002, 8:12am UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/1 "2002-07-31T08:12:25Z")
Take a situation when areas of the world broke off from their ‘motherland’ - i.e. The Japanese Islands, Papua New Guinea from Australia etc… Were these events something dragged out over millennia OR would they have been massive, violent events witnessable by primitive humans of the day? (Would there have been humans in the timescale of the main breaking up?) Did the land crumble like in an earthquake, or was it more of an ‘erosion over time’ phenomenon? I know the plates in that area area curently moving at about 8-9cm per year relative to each other. From [here.](http://www.jnc.go.jp/kaihatu/tisou/zh12/h12/s01/pdf/02-02-01.pdf) (- Warning, PDF file). A book I am reading said humans migrated to these islands _before_ they broke up to be separate entities, but any cites seem to say it happened about 15 million years ago. Homo Sapiens seems to have life from, say 120 kya. So, what’s the dope? Thanks… ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [July 31, 2002, 12:43pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/2 "2002-07-31T12:43:14Z")
Plate Tectonics and human migration don’t take place on the same time scale. Hominid migrations involving pre-humans are only peripherally involved with the separation of land masses from each other, and that generally involves the closure of narrow barriers such as straits and isthmuses, more often as a result of glacial actions, or volcanic events than plate movements. It is far more likely that early hominid species crossed narrow seas by the same chance methods as other animals, such as rafting, or swimming. The glacial fluctuations of the later ice ages caused many changes in shore lines, and the connection of previously isolated islands to the mainland. Humans would certainly have made use of such access, when it occurred. Most of the early history of our species took place during these glacial, and interglacial periods. ## Tris “What have you done to that cat? It looks half dead!” ~ Mrs. Erwin Schrodinger ~ ---
**Author:** ![Aro](https://avatars.discourse-cdn.com/v4/letter/a/b3f665/32.png) [@Aro](https://boards.straightdope.com/u/Aro)\ **Post date:** [July 31, 2002, 1:30pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/3 "2002-07-31T13:30:07Z")
Thanks, **Trisk**. I guess I had two questions mingled in there. Looks like the book I was reading was er…talking nonsense…with respect to human migration. Unless it were, as you mention, surmising that humans crossed ice floes to the islands. There was certainly no mention of boats in the book. (It is a book with focus on the _Economic_ History of man, so we can forgive it for ‘glossing’ over many ‘facts’ on pre-human movements) But, with regard to the mechanics of plate tectonics… would the event have been gradual or immediate, regardless of whether it was witnessed? Or is it just impossible to know? ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [July 31, 2002, 1:43pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/4 "2002-07-31T13:43:51Z")
> [@](#): > > \*Originally posted by Aro \* > \*\* > Were these events something dragged out over millennia OR would they have been massive, violent events witnessable by primitive humans of the day? > > Thanks… \*\* The Horn of Africa is currently beging pulled away from the continent along the Rift Valley. There is a constantly increasing underground flow of sea water from the Red Sea into the valley. The separation is measurable and is constantly watched. It was the subject of a TV documentary (Discovery, A&E, National Geographic ?) a couple of years ago. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [July 31, 2002, 1:47pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/5 "2002-07-31T13:47:06Z")
> [@](#): > > \*Originally posted by Aro \* > \*\* > Were these events something dragged out over millennia OR would they have been massive, violent events witnessable by primitive humans of the day? > > Thanks… \*\* The Horn of Africa is currently being pulled away from the continent along the Rift Valley. There is a constantly increasing underground flow of sea water from the Red Sea into the valley. The separation is measurable and is constantly watched. It was the subject of a TV documentary (Discovery, A&E, National Geographic ?) a couple of years ago. ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [July 31, 2002, 2:29pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/6 "2002-07-31T14:29:43Z")
When New Guinea separated from Australia, it wasn’t millions of years ago by plate tectonics, but thousands of years ago by sea levels rising when glaciers melted at the end of the ice age. In other words, New Guinea didn’t go anywhere, but the sea rose to cut it off from Australia. Before that time people could walk from New Guinea to Australia, but they would have had to take a boat from Asia to New Guinea. As **Triskadecamus** said, plate tectonics hasn’t had much, if anything, to do with human migration, so when the book refers to islands separating after people got there, its probably referring to rising sea levels covering land bridges. ---
**Author:** ![thewiz](https://avatars.discourse-cdn.com/v4/letter/t/6de8d8/32.png) [@thewiz](https://boards.straightdope.com/u/thewiz)\ **Post date:** [July 31, 2002, 2:41pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/7 "2002-07-31T14:41:06Z")
To answer the OP: plate tectonics happens VERY slowly over thousands or millions of years. Land shifts are measurable but are in the order of millimeters or centimeters per year. You wouldn’t get cataclysmic events from plate shifts. HOWEVER, other natural events associated with tectonics do occur. For example, the “Ring of Fire” surrounding the Pacific Ocean is related to plate tectonics. Volcanoes and earthquakes are associated with fault lines where plates meet. Mountains are created when 2 plates meet and one rides over another. ---
**Author:** ![JS\_Princeton](https://avatars.discourse-cdn.com/v4/letter/j/57b2e6/32.png) [@JS\_Princeton](https://boards.straightdope.com/u/JS_Princeton)\ **Post date:** [July 31, 2002, 2:42pm UTC](https://boards.straightdope.com/t/breaking-up-of-continents-plate-movement/121663/8 "2002-07-31T14:42:20Z")
Catastrophism went through a time when it was completely laughed at. Now with the mild fringe respectability given to Punctuated Equilibrium, some are beginning to wonder if, say, the Black Sea filled up extremely quickly past the straights of Bosporus. These are delicate issues and not easily answered. Still, we are nearly certain that catastrophism and plate tectonics are mutually exclusive.