Showing posts with label rocks. Show all posts
Showing posts with label rocks. Show all posts

January 29 - Happy Birthday, Frederick Mohs

    Posted on January 29, 2022


This is an update of my post published on January 29, 2011:




The German geologist Frederick Mohs is most famous for his Scale of Hardness. 

A geologist is a scientist who studies rocks and minerals and the origin and structure of the earth. So it may not surprise you to learn that Mohs's Scale of Hardness concerns rocks and minerals! 

Talc - 1
Born on this day in 1773, Mohs compared the hardness of various minerals, comparing each to the others by scratching one mineral onto another. Obviously, a harder material can scratch a softer one, but a softer material cannot scratch a harder one. Using his comparative data, Mohs created a scale that goes from one of the softest minerals, talc, at Number 1, to the hardest mineral, diamond, at Number 10. Of course, some minerals fall between the numbers and can be expressed as a decimal. For example, tin is considered 1.5. Also, the hardness of non-minerals can be expressed using the Mohs Scale; fingernails are about 2.5, for example, and glass runs from 5 to 6.

Diamond - 10





Malachite (above) and azurite (below) both
score between 3.5 and 4 on the Mohs Scale.





Amethyst - 7
Check out this short video about the Mohs Scale.  

 


Explore gems and minerals at the Smithsonian website.


The Hope Diamond can be seen at the Smithsonian

 


July 26 - Rock Day

 Posted on July 26, 2021


This is an update of my post published on July 26, 2010:


On this day in 1943, rock great Mick Jagger was born in England. He became the lead singer of the Rolling Stones and is also a songwriter, music producer, and even occasional actor.




AND:

On this day in 1969, scientists got their first look at moon rocks returned by the crew of Apollo 11.


Learn about rock as in rock-and-roll music.

This website gives some early history of “rock and roll,” with plenty of links to explore further.




Learn about rocks as in actual, you know, rocks. Geology and stuff.

I love love love the book Everybody Needs a Rock, by Byrd Baylor, with wonderful illustrations by Peter Parnall.




Start a rock collection, or add to one you've already begun. You can pick up pretty rocks you find in nature (except of 
course in protected areas and wilderness preserves), and you can also buy rocks. Arts-and-crafts stores often sell small polished stones, and there are rock shops in some areas. We found a “rock guy” who lives near us and has a rather wildly unkempt yard FULL of rocks. He is super enthusiastic and knowledgeable, and he has sold us some great rocks and geodes at very reasonable prices.





Here is a website for kids who collect rocks.

June 3 - Happy Birthday to the Father of Modern Geology

 Posted on June 3, 2021

This is an update of my post published on June 3, 2010:



Born this day in 1726, in Edinburgh, Scotland, James Hutton grew up to be a physician, naturalist, chemist, and experimental farmer. But he is most famous for his work as a geologist. 

His contributions to geology are so imporant, Hutton is often called "the Father of Modern Geology." They include the idea that the Earth's rocks were created from materials laid down in early oceans—dirt and sand and the shells and bones of living creatures—and that these rocks were later uplifted into their current place above sea level.

Hutton suggested that this rock-building process has gone on for a long time, and that today's rocks are continuing to erode and wash out to sea, creating the rocks of the future.


With this ongoing process of rock formation, Hutton made the case for the Earth being much, much older than most people had suspected.




Hutton was a famously bad writer.


Want a sample? Here's one:
“The world which we inhabit is composed of the materials, not of the earth which was the immediate predecessor of the present, but of the earth which, in ascending from the present, we consider as the third, and which had preceded the land that was above the surface of the sea, while our present land was yet beneath the water of the ocean.”
Yet he is credited with a nice turn of phrase here:
"(In geology) we find no vestige of a beginning—no prospect of an end."

Before Hutton...


... most people had supposed that the bedrock beneath our feet had been around since the beginning of the world, or perhaps since a single enormous flood a few thousand years ago.


But Hutton's analysis of the composition of sedimentary rocks showed that there had been at least several cycles of erosion - rock formation - uplift, and possibly many, many cycl
es.

Hutton proposed that Earth was hot in its interior, and that the planet was millions rather than thousands of years old. (He was right about Earth's interior being hot, but our planet's age actually numbers in the billions of years. Still, Hutton's estimate was a huge improvement over earlier ideas.)



We can often see layers
in sedimentary rocks.










The Rock Cycle
 
Hutton's discovery about the rock cycle largely deals with sedimentary rocks and metamorphic rocks. Sedimentary rocks are created when layers of dirt, sand, and remnants of life are pushed down over the years into hard rocks. Metamorphic rocks are usually sedimentary rocks that have been changed by extreme heat or pressure.

Here is a cartoon-illustrated explanation of the rock cycle.

 

Here is a video about how different kinds of rocks form.


Here is a wacky activity: making an edible "sedimentary rock."

 


Also on this date:
















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