the Igneous Rocks

I bet the sediments said they were the best. Which that aren't. Igneous rocks are way cooler. We aid volcanoes and tell their history. Way better than some old bug or something.

[the-igneous-blog]

Plutons!

You mentioned plutons! You have to explain those!

[what-do-i-know-about-geolog-blog]

*sighs* Fine, fine, go ahead….

[the-igneous-blog]

Yes!

Plutons, what are they? They’re rock intrusions, it’s when magma cools underground (also another name for intrusive igneous rock). They can be like sheets or just massive. 

A few examples of plutons:

Look at this dyke. It clearly goes through the layers and obviously has to younger than the rocks around it (AKA country rock).

What about this? There’s metamorphic rock surrounding the pluton. How’d that happen? I guess the metamorphic would have to have formed and then the pluton broke through…

And check out these xenoliths. They’re just pieces from the country rock that broke off and decided to mix with the pluton, but they’re haven’t melted yet. 

Obviously, there are many more kinds of plutons, like batholiths, sill, laccolith…

[what-do-i-know-about-geolog-blog]

BUT, we need to move. What’s next?

[the-igneous-blog]

*sputters* Next?! But there’s so much more to talk about…. Fine! We’ll do volcanoes! I have to talk about those!

[the-igneous-blog]

Volcanoes

So, volcanoes form when plates converge. The subducting plate melts and provides magma for the volcano. 

Main types of volcanoes:

Shield: It’s flat, wide, it’s basically layers of layers of lava piled and dried on top of each other. It’s mafic, so it’s lava has a very low viscosity, which means liquid-ish. 

Here’s one from Hawaii:

Strato volcano/Composite volcano: It’s alternated layers of lava and pyroclastic material (volcano remains). Very explosive and it’s magma is very high viscosity. So, thick, molasses-like lava.

Take a look at Mt. Rainier:

and cinder cones: they’re completely made up of pyroclastic material, rock fragments, so it’s like a perfect cone shape. It can have any type of lava, and it’s only semi explosive.

Speaking of which, why are volcanoes explosive? Because they get all clogged up with magma and that causes pressure to rise. Eventually the pressure gets too high and it just has to blow! 

Now, there’s also fissure eruptions…

[what-do-i-know-about-geolog-blog]

And we don’t need to hear it! Seriously, we need to get on to other stuff…

[the-igneous-blog]

What other stuff?! We’re already done!

[the-metamorphic-blog]

Give it a rest, why don’t you?

[the-igneous-blog]

Are you mocking me?!

[the-igneous-blog]

Volcanoes

So, volcanoes form when plates converge. The subducting plate melts and provides magma for the volcano. 

Main types of volcanoes:

Shield: It’s flat, wide, it’s basically layers of layers of lava piled and dried on top of each other. It’s mafic, so it’s lava has a very low viscosity, which means liquid-ish. 

Here’s one from Hawaii:

Strato volcano/Composite volcano: It’s alternated layers of lava and pyroclastic material (volcano remains). Very explosive and it’s magma is very high viscosity. So, thick, molasses-like lava.

Take a look at Mt. Rainier:

and cinder cones: they’re completely made up of pyroclastic material, rock fragments, so it’s like a perfect cone shape. It can have any type of lava, and it’s only semi explosive.

Speaking of which, why are volcanoes explosive? Because they get all clogged up with magma and that causes pressure to rise. Eventually the pressure gets too high and it just has to blow! 

Now, there’s also fissure eruptions…

[what-do-i-know-about-geolog-blog]

And we don’t need to hear it! Seriously, we need to get on to other stuff…

[the-igneous-blog]

What other stuff?! We’re already done!

[the-igneous-blog]

Volcanoes

So, volcanoes form when plates converge. The subducting plate melts and provides magma for the volcano. 

Main types of volcanoes:

Shield: It’s flat, wide, it’s basically layers of layers of lava piled and dried on top of each other. It’s mafic, so it’s lava has a very low viscosity, which means liquid-ish. 

Here’s one from Hawaii:

Strato volcano/Composite volcano: It’s alternated layers of lava and pyroclastic material (volcano remains). Very explosive and it’s magma is very high viscosity. So, thick, molasses-like lava.

Take a look at Mt. Rainier:

and cinder cones: they’re completely made up of pyroclastic material, rock fragments, so it’s like a perfect cone shape. It can have any type of lava, and it’s only semi explosive.

Speaking of which, why are volcanoes explosive? Because they get all clogged up with magma and that causes pressure to rise. Eventually the pressure gets too high and it just has to blow! 

Now, there’s also fissure eruptions...

[the-igneous-blog]

Plutons!

You mentioned plutons! You have to explain those!

[what-do-i-know-about-geolog-blog]

*sighs* Fine, fine, go ahead….

[the-igneous-blog]

Yes!

Plutons, what are they? They’re rock intrusions, it’s when magma cools underground (also another name for intrusive igneous rock). They can be like sheets or just massive. 

A few examples of plutons:

(picutre of intrusion)

Look at this dyke. It clearly goes through the layers and obviously has to younger than the rocks around it (AKA country rock).

(another pic of intrusion)

What about this? There’s metamorphic rock surrounding the pluton. How’d that happen? I guess the metamorphic would have to have formed and then the pluton broke through…

(xenoliths)

And check out these xenoliths. They’re just pieces from the country rock that broke off and decided to mix with the pluton, but they’re haven’t melted yet. 

Obviously, there are many more kinds of plutons, like batholiths, sill, laccolith…

[what-do-i-know-about-geolog-blog]

BUT, we need to move. What’s next?

[the-igneous-blog]

*sputters* Next?! But there’s so much more to talk about.... Fine! We’ll do volcanoes! I have to talk about those!

[the-igneous-blog]

Plutons!

You mentioned plutons! You have to explain those!

[what-do-i-know-about-geolog-blog]

*sighs* Fine, fine, go ahead….

[the-igneous-blog]

Yes!

Plutons, what are they? They’re rock intrusions, it’s when magma cools underground (also another name for intrusive igneous rock). They can be like sheets or just massive. 

A few examples of plutons:

(picutre of intrusion)

Look at this dyke. It clearly goes through the layers and obviously has to younger than the rocks around it (AKA country rock).

(another pic of intrusion)

What about this? There’s metamorphic rock surrounding the pluton. How’d that happen? I guess the metamorphic would have to have formed and then the pluton broke through…

(xenoliths)

And check out these xenoliths. They’re just pieces from the country rock that broke off and decided to mix with the pluton, but they’re haven’t melted yet. 

Obviously, there are many more kinds of plutons, like batholiths, sill, laccolith…

[the-igneous-blog]

BUT, we need to move on. What’s next?

[the-igneous-blog]

Plutons!

You mentioned plutons! You have to explain those!

[what-do-i-know-about-geolog-blog]

*sighs* Fine, fine, go ahead….

[the-igneous-blog]

Yes!

Plutons, what are they? They’re rock intrusions, it’s when magma cools underground (also another name for intrusive igneous rock). They can be like sheets or just massive. 

A few examples of plutons:

Look at this dyke. It clearly goes through the layers and obviously has to younger than the rocks around it (AKA country rock).

What about this? There’s metamorphic rock surrounding the pluton. How’d that happen? I guess the metamorphic would have to have formed and then the pluton broke through...

And check out these xenoliths. They’re just pieces from the country rock that broke off and decided to mix with the pluton, but they’re haven’t melted yet. 

Obviously, there are many more kinds of plutons, like batholiths, sill, laccolith...

[the-igneous-blog]

Plutons!

You mentioned plutons! You have to explain those!

[the-metamorphic-blog]

Is it my turn yet?

We finished with igneous rocks! Can I go now?

[the-igneous-blog]

Hey! I only had, like 2 posts! We still need to talk about the plutons, the volcanoes, plate tectonics…

[the-metamorphic-blog]

That’s going to take FOREVER.

[the-igneous-blog]

Too bad! Wait your turn!

So plutons are intrusions in the bedding from a magma plume, sometimes lead into volcanoes…

[what-do-i-know-about-geolog-blog]

We’re going to start with metamorphic rocks now.

[the-igneous-blog]

But, but....

[the-metamorphic-blog]

Is it my turn yet?

We finished with igneous rocks! Can I go now?

[the-igneous-blog]

Hey! I only had, like 2 posts! We still need to talk about the plutons, the volcanoes, plate tectonics…

[the-metamorphic-blog]

That’s going to take FOREVER.

[the-igneous-blog]

Too bad! Wait your turn!

So plutons are intrusions in the bedding, sometimes lead into volcanoes...

[the-metamorphic-blog]

Is it my turn yet?

We finished with igneous rocks! Can I go now?

[the-igneous-blog]

Hey! I only had, like 2 posts! We still need to talk about the plutons, the volcanoes, plate tectonics...

[the-igneous-blog]

*deeps breaths*

Okay, so where was I? 

Extrusive rocks. Those are the volcanic rocks. They are very fine-grained, because they cooled quickly, reason why? They are a result of cooling lava. The difference between lava and magma?

Magma is the stuff underground flowing beneath the Earth’s crust while lava is the stuff that spews out of volcanoes.

So extrusive rocks have very fine crystals. Intrusive is the opposite. Coarse, large crystals, made from magma.

[he-who-knows-all-geo-blog]

Another way for igneous rocks to form is with fractional crystallization, however this is only within a magma pool/pluton. With fractional crystallization, the early crystals start to settle out of the melt and more crystals just continue to settle on top. 

The order follows Bowen’s Reaction series, so because olivine cools at a higher temperature, it would settle first, then pyroxene, amphibole, etc.

[the-igneous-blog]

Oh! and another thing, with igneous rocks, mineral composition matters. A lot. Depending on it’s percentage of say, feldspar or ferromagnesian, it determines whether or not a rock is felsic or mafic. 

This matters because with it, we can determine the past. (Law of Uniformitarianism, anybody?) We can figure out what a volcano used to be like even if it’s dead now.

[the-igneous-blog]

*deeps breaths*

Okay, so where was I? 

Extrusive rocks. Those are the volcanic rocks. They are very fine-grained, because they cooled quickly, reason why? They are a result of cooling lava. The difference between lava and magma?

Magma is the stuff underground flowing beneath the Earth’s crust while lava is the stuff that spews out of volcanoes.

So extrusive rocks have very fine crystals. Intrusive is the opposite. Coarse, large crystals, made from magma.

[what-do-i-know-about-geolog-blog]

Igneous rocks it is!

Alright, so igneous rocks! How are they made?

[the-igneous-blog]

OO! I know!

[the-metamorphic-blog]

Sheesh, chill out, why don’t you? It’s just the intro.

[the-igneous-blog]

You’re just jealous!

Igneous rocks are formed when magma cools and crystallizes. There are actually two different of igneous rocks, extrusive and intrusive. Another name for them is volcanic and plutonic rocks. Extrusive are…

[ignorant-existence-blog]

Wait! What’s magma again?

[the-igneous-blog]

...

[what-do-i-know-about-geolog-blog]

Igneous rocks it is!

Alright, so igneous rocks! How are they made?

[the-igneous-blog]

OO! I know!

[the-metamorphic-blog]

Sheesh, chill out, why don’t you? It’s just the intro.

[the-igneous-blog]

You’re just jealous!

Igneous rocks are formed when magma cools and crystallizes. There are actually two different of igneous rocks, extrusive and intrusive. Another name for them is volcanic and plutonic rocks. Extrusive are...

[what-do-i-know-about-geolog-blog]

Igneous rocks it is!

Alright, so igneous rocks! How are they made?

[the-igneous-blog]

OO! I know!

[what-do-i-know-about-geolog-blog]

How do you classify different types of rock?

How? Well, you should know that there are three different types of rocks that we mainly talk about. 

Sedimentary. 

Igneous

Metamorphic.

There are the three kinds of rocks that circle the Rock Cycle. And, if you’ve been paying attention, you would know we’ve already talked quite a bit about sedimentary rocks. So, if you need a review, sedimentary rocks are formed by weathering and erosion. If you need to know the types, go back through the blog. Just turn around. Stop right now.

That just leaves the metamorphic rocks, and the igneous rocks. But which to start with, hmm…

[the-metamorphic-blog]

ME!

[the-igneous-blog]

Ah, excuse me?