Monday, October 10, 2011

Dr. A's course in geology

Glossary: to be updated as needed

#1 Minerals & Rocks: Definitions

Pressie's definitions.

#2 Silicate Minerals

#3 Rocks: Igneous, Sedimentary, Metamorphic

Comment so far: I've already picked up a fair amount of this information from my own internet researches on geological questions, but it gets more detailed than I have an interest in learning, so I'll just keep the posts for reference in case they're useful later.

My overall impression of Dr. A's teaching style is that he's doing a good job. But he doesn't explain enough for the novice. For instance, we need more of a definition of felsic and mafic. What does a felsic or mafic mineral look like? How would I recognize it in the field? Such words should be defined more than once in such a study if we are to really learn what they mean.

Similarly, putting up a chart with names of minerals doesn't help the person who isn't familiar with those things in the real world. I've many times looked up rocks and minerals myself to see pictures of them, and in a study like this one you should at least give links to pictures since you can't bring the objects to school to pass around. Names are meaningless without some idea of what they look like in reality.

The only controversial point so far is in the Rock Cycle diagram in #3 on the three classes of rocks. There's no problem with the basic formation of the rocks, knowing them by their history, only with 1) the implication that the earth repeats this cycle over and over to account for the millions of years of the assumptions of establishment geology, and with 2) the implication that sedimentary rocks of the vast extent we see in the Geologic Column could have been formed by the small local processes implied.

Here's a page geared to children on the subject of the Rock Cycle, with the parts a creationist would question bolded:
The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly.

When it pours out on Earth's surface, magma is called lava. Yes, the same liquid rock matter that you see coming out of volcanoes.

On Earth's surface, wind and water can break rock into pieces. They can also carry rock pieces to another place. Usually, the rock pieces, called sediments, drop from the wind or water to make a layer. The layer can be buried under other layers of sediments. After a long time the sediments can be cemented together to make sedimentary rock. In this way, igneous rock can become sedimentary rock.
In principle I suppose there's nothing wrong with this description, except that it implies that such slow and unpredictable processes could have formed the vast rock layers of the Geologic Column, which is just plain impossible.
All rock can be heated. But where does the heat come from? Inside Earth there is heat from pressure (push your hands together very hard and feel the heat). There is heat from friction (rub your hands together and feel the heat). There is also heat from radioactive decay (the process that gives us nuclear power plants that make electricity).

So, what does the heat do to the rock? It bakes the rock.

Baked rock does not melt, but it does change. It forms crystals. If it has crystals already, it forms larger crystals. Because this rock changes, it is called metamorphic. Remember that a caterpillar changes to become a butterfly. That change is called metamorphosis. Metamorphosis can occur in rock when they are heated to 300 to 700 degrees Celsius.

When Earth's tectonic plates move around, they produce heat. When they collide, they build mountains and metamorphose (met-ah-MORE-foes) the rock.

The rock cycle continues. Mountains made of metamorphic rocks can be broken up and washed away by streams. New sediments from these mountains can make new sedimentary rock.
Sure, on a small scale, but not on the scale of the Geologic Column. And the idea that any mountain has ever eroded down to the flat plains so often shown in geological diagrams, nothing but wild theory. Never happened. Couldn't even really happen with millions of years to accomplish it.
The rock cycle never stops.
So ALL the rocks ALWAYS get recycled according to this theory and the earth is just being constantly changed from one to the other. Highly unlikely. Of course in principle they no doubt can and do go through all the changes illustrated, but not any great proportion of them as imagined by Old Earth geology.

As usual, among the facts that really are facts and the science that really is science there is this indigestible lump of theory or really, bald assumption, that's just *there* with nothing to support it, no discussion of it. Will Dr. A at some point address the question "How do we know?" with respect to this?

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