Naked Science Forum

Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Herman Melville on 30/06/2009 11:46:56

Title: Are all of Earth's rocks getting smaller all the time?
Post by: Herman Melville on 30/06/2009 11:46:56

With erosion, quarrying, and general wear and tear, rocks above the surface can only be getting smaller. Are new rocks formed by volcanic activity or do lava formations not count?

Are the days of big rocks numbered?
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.visitsouthwest.co.uk%2Fimages%2Fproducts%2F16644_1.jpg&hash=884e20d2c3778e9bd82d8597a632db07)

Title: Are all of Earth's rocks getting smaller all the time?
Post by: neilep on 30/06/2009 14:57:20

What a great question. As a sheepy I of course know sod-all about rocks !  [;D]

My best guess is that new rocks are indeed being replaced as cliffs erode and collapse to make new big rocks. I would think your suggestion regarding volcanic activity is spot on though.

What we need is some rockologists...I think a few frequent the site.....I know of at least two peeps who pose as rock experts..JimBob & Bass !

Herman, would you like me to move this thread to the geology section for ewe ?

Title: Are all of Earth's rocks getting smaller all the time?
Post by: RD on 30/06/2009 15:06:26

Small grains of rock become bigger metamorphic (http://en.wikipedia.org/wiki/Metamorphic_rock) rocks.

Title: Are all of Earth's rocks getting smaller all the time?
Post by: Bass on 30/06/2009 18:25:35

Rocks are recycled.

Part of recycling is, as RD suggests, adding heat and pressure to those smaller grains (sediments) and creating new rocks, whether by metamorphism or by lithifying them into sedimentary rocks. 

Volcanoes count!  The most effusive volcanoes are the mid-oceanic ridges.  New volcanic rocks are created there, slowly drift across the ocean floors and are then devoured by subduction.

Parts of the crust are being uplifted, whether by plate tectonics, hot spots, faulting or isostatic rebound.  If not for uplift, we would all live in a water-world and have gills and webbed toes like Kevin Costner.  Uplift and erosion battle to control the shape of the land.

Lest we not forget the cosmologists[;D] on this forum, material is also constantly bombarding us from space.

Title: Are all of Earth's rocks getting smaller all the time?
Post by: Herman Melville on 07/07/2009 15:03:25

Thanks. I feel much happier now that I know they're not all getting smaller all the time.