# The Earth's crust 20% sponge? **URL:** \ **Category:** Factual Questions\ **Created:** [July 26, 2006, 3:08pm UTC](https://boards.straightdope.com/t/the-earths-crust-20-sponge/366093 "2006-07-26T15:08:56Z")\ **Posts on this page:** 4\ **Page:** 2
**Author:** ![EvilTOJ](https://avatars.discourse-cdn.com/v4/letter/e/ee59a6/32.png) [@EvilTOJ](https://boards.straightdope.com/u/EvilTOJ)\ **Post date:** [August 5, 2011, 6:18am UTC](https://boards.straightdope.com/t/the-earths-crust-20-sponge/366093/21 "2011-08-05T06:18:43Z")
Imagine how much deeper the oceans would be without it! ---
**Author:** ![mac\_bolan00](https://avatars.discourse-cdn.com/v4/letter/m/b3f665/32.png) [@mac\_bolan00](https://boards.straightdope.com/u/mac_bolan00)\ **Post date:** [August 5, 2011, 6:35am UTC](https://boards.straightdope.com/t/the-earths-crust-20-sponge/366093/22 "2011-08-05T06:35:43Z")
if the crust were a sponge, imagine how much water the earth is holding! ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [August 5, 2011, 9:50am UTC](https://boards.straightdope.com/t/the-earths-crust-20-sponge/366093/23 "2011-08-05T09:50:22Z")
> [@santallum](#): > > Its perhaps suprising that Fry did not mention that SiO2 is glass is quartz is flint is chert is chalcedony is chrysoprase is jasper is amethyst (etc) , as all these things are the different forms of the same chemical compound Silicon Dioxide .. marvelous stuff That depends on what your definition of “is” is… quartz is SiO[sub]2[/sub], yes, but it’s not \*just \*that - it’s SiO[sub]2[/sub] _with a specific crystal structure_. You can’t compare it to chalcedony, you need to compare it to e.g. moganite or cristobalite. Just like jasper, for instance, isn’t \*just \*SiO[sub]2[/sub] either - it has to be opaque, and coloured by inclusions. Granted, there’s no \*clear \*distinction between some of these categories - is a given piece flint or chert, for instance? Well, if it’s microcrystalline, it’s \*always \*chert, but it’s also flint _if it’s found in chalk or marl_. For some of them, there’s a great degree of specificity, and for others, while there’s some leeway, it’s not infinite. Basically, there’s a degree of mixing-up of minerals (e.g. quartz, moganite) with rocks (e.g. chert, chalcedony) with subtypes of both(e.g. amethyst is a _kind of_ quartz, flint is a _kind of_ chert) happening. ---
**Author:** ![furryman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/furryman/32/99_2.png) [@furryman](https://boards.straightdope.com/u/furryman)\ **Post date:** [August 6, 2011, 4:47pm UTC](https://boards.straightdope.com/t/the-earths-crust-20-sponge/366093/24 "2011-08-06T16:47:39Z")
Combine that with the 20% of people named Bob and you get… [Previous page](https://boards.straightdope.com/t/the-earths-crust-20-sponge/366093.md?page=1)