# Liquid Rock (DD-298)

> Lava is molten rock erupted at the surface; underground, the same material is called magma. Most magma forms in the upper mantle, and a key way rock melts there is decompression: as hot mantle rises, the pressure on it drops and it partly melts, which is why mid-ocean ridges and hotspots such as Iceland and Hawaii are so volcanic. Erupted lava typically ranges from about 700 to 1,200 °C (1,300 to 2,200 °F). Runny basaltic lava can travel quickly, while silica-rich lava is thick and slow. As it cools, lava can crack into hexagonal basalt columns or build up islands. The footage is drone video of lava fountaining and flowing in Iceland.

- Department: Nature (also Science)
- First published: 2024-08-14
- Last updated: 2024-08-14
- Permalink: https://detailenjoyer.com/case/liquid-rock/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-298-F01**: Lava typically ranges from 700 to 1,200 °C. _(Write-up · Exhibit C (Temperature))_
- **DD-298-F02**: Rising mantle rock melts as pressure drops. _(Write-up · Exhibit B (Decompression melting))_

## Write-up

Lava can flow at 1,200 °C. Most mantle melting happens when pressure drops, not when it rises.

1. **Magma at the surface**: Lava is molten rock erupted at the surface.
2. **Decompression melting**: Rising mantle rock partly melts as pressure drops.
3. **Temperature**: Lava typically ranges from about 700 to 1,200 °C.
4. **Runny or thick**: Basaltic lava flows easily; silica-rich lava is thick and slow.
5. **Cooling shapes**: Cooling lava can form basalt columns and islands.

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## Reel vs. record

- **Note**: 'Intense heat and pressure cause rock to melt': I'd flip the pressure part. Higher pressure tends to keep rock solid; much mantle melting happens when pressure drops as rock rises.

## Video: Liquid Rock: Lava Can Flow at 1,200 °C

- Duration: 27.0 s · Published: 2024-08-14
- File: https://detailenjoyer.com/assets/videos/C-ozQnYu6iB.mp4

### Transcript

DID YOU KNOW? Lava is molten rock expelled by a volcano during an eruption. It originates from the Earth's mantle where intense heat and pressure cause rock to melt. When lava reaches the surface it can flow at varying speeds depending on its composition and temperature. The temperature of lava typically ranges between 700 to 1,200 degrees Celsius or 1,300 to 2,200 degrees Fahrenheit. The flow and cooling of lava can create various geological formations such as basalt columns and volcanic islands. NOW YOU KNOW!

## Questions & answers

**Q: What's lava called underground?**  
A: It becomes lava when it erupts. _(Source: Write-up · Exhibit A (Magma at the surface) · Wikipedia: Lava)_

**Q: What triggers decompression melting?**  
A: Rising mantle rock partly melts. _(Source: Write-up · Exhibit B (Decompression melting) · Wikipedia: Lava)_

**Q: What's lava's typical temperature range?**  
A: That's 1,300 to 2,200 °F. _(Source: Write-up · Exhibit C (Temperature) · Wikipedia: Lava)_

**Q: Which lava flows most easily?**  
A: It has less silica. _(Source: Write-up · Exhibit D (Runny or thick) · Wikipedia: Lava)_

**Q: What can cooling lava form?**  
A: It cracks into columns. _(Source: Write-up · Exhibit E (Cooling shapes) · Wikipedia: Lava)_

## Sources

- [Wikipedia: Lava](https://en.wikipedia.org/wiki/Lava)

## Cite this case file

Easterling, Marcus. "Liquid Rock." The Detail Department (DetailEnjoyer), case file DD-298, last updated Aug 14, 2024. https://detailenjoyer.com/case/liquid-rock/