Questions tagged [magmatism]

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1answer
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Why the “Mission to Earth’s core” proposal suggests using liquid iron instead of lead?

Nature communications article "Mission to Earth's core — a modest proposal", suggests placing a large volume of liquid iron in a crack and let it sink all the way to the Earth's core, carrying along a ...
3
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1answer
40 views

Heating and cooling a non-magnetic iron ore causes it to become magnetic?

I'm a potter. I find what I think are iron concretions in a deep red local clay. I fired these iron concretions to cone 6 (about 2100F) and when I removed it from the kiln (room temp) they were then ...
3
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1answer
226 views

What is the difference between subvolcanic rocks and plutonic rocks?

I'm studying Plutonic (Intrusive) rocks and I really don't understand the difference between Plutonic Rocks that form in Sills and Dikes from the so called subvolcanic rocks, also known as a ...
2
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2answers
355 views

Water and explosive volcanoes in the Pacific ring of fire

Most volcanoes in the Pacific Ring of Fire have an explosive nature. This is due to high concentrations of water in their magma. Obviously, this magma comes from several kilometres below the earth's ...
4
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0answers
78 views

What causes a change in composition from basanite to nephelinite?

Can the change in composition from basanite to nephelinite (i.e. increasing alkalis with decreasing SiO2) be explained in terms of fractional crystallisation, or only by a decreasing degree of partial ...
5
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1answer
257 views

Why does the loss of water from a felsic magma encourage crystallisation?

Felsic magmas crystallise in the crust, unlike mafic magmas which tend to make it to the Earth's surface, for the following reasons: They are more viscous than mafic magmas and therefore it is ...
5
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2answers
74 views

Why is ignimbrite associated with felsic magmas?

Why is ignimbrite associated with only more felsic magmas?
7
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1answer
129 views

Cooling time of basalt flows?

In places like the Giant's causeway in Ireland (Antrim basalts) there are columnar basalt flows of 100 metres or more. I'm aware that the cooling mechanism is complex, but is there any rough and ready ...
6
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1answer
2k views

Does Magnetic Deviation depend on altitude?

Magnetic declination, sometimes called magnetic variation, is the angle between magnetic north and true north. Declination is positive east of true north and negative when west. Magnetic ...
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0answers
211 views

What is solidus and liquidus temperature of granite?

My understanding is that because a rock is composed of variety of minerals, so it does not have fix melting point, rather there is a range below which whole rock is solid and above which whole rock is ...
2
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2answers
53 views

Which equations describe complete (or near complete) behaviour of magma moving through rocks?

Yes this is a bit broader question but I want to know which processes play their role in movement of magma. If one wants to model magma movement through rocks, which processes should one not miss at ...
3
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1answer
319 views

Relative dating of intrusion

I am quite new to geology and have a realtive dating problem which I am a bit unsure of. I know very well the principle of superposition, principle of cross-cutting, etc., but am still a little bit ...
8
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1answer
136 views

Melting basalt on the lunar surface - what would the resulting material be like?

The idea is to melt the fine-grain portion of basalt regolith using a large Fresnel lens, and let it cool to a solid. The lens would track along a tamped bed of material leaving a molten puddle ...
3
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1answer
117 views

Do discordants dykes ever travel concordantly (are transgressive dykes a thing)?

Transgressive sills "jump" between bedding planes, following joints: ...
2
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1answer
196 views

Volcano magma chamber [duplicate]

If I use a really big drill and drill all the way down to a magma chamber what exactly would happen? From what I understand we cant drill to a Magma Chamber because it is really hot, but I have a ...
4
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1answer
70 views

Do the rocks below an active sill go down, or those above go up, or both?

Having read a little about sill formations like the Palisades Sill (eastern USA) and Whin Sill (UK), I understand that strata became separated by the injected layer of magma, with monumental ...
6
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1answer
389 views

Can a cosmic impact break Earth's crust in large area exposing the magma ocean?

Can a cosmic impact event break the Earth's surface in such a way so it expose liquid magma over large areas with solid rocks floating in it as "icebergs"? I wonder, will such magma ocean experience ...
18
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3answers
4k views

Why don't scientists use fire entry suits to study volcanoes?

It seems like the only personal protective equipment (PPE) that volcanologists use are aluminized suits that don't provide any protection from direct contact with lava, making an unexpected splash ...
10
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2answers
1k views

Why are alkali basalts found at rifting centres and on top of 'plumes', whereas MORBs are generally tholeiitic?

So I was essentially wondering why it was that the basalts on top of 'plumes' at 'hotspots' (sometimes called OIBs, ocean island basalts) and at continental rifting centres are enriched in alkaline ...
7
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1answer
151 views

Is there an earth science discipline, or subdiscipline, that only studies magma or lava?

I know volcanologists study volcanoes. Is there a subdiscipline that only studies maga or lava? A magmatologist?
19
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3answers
996 views

What are rare earths and why do they cluster near alkaline magmatism?

'Rare earths' play a vital role in the modern economy, and they are becoming more of a point of focus in geopolitical realms. What are 'rare earths' and why do they appear to cluster in association ...