VOLCANIC ROCKS

VOLCANIC ROCKS

Luisa Miguel López and Daniela Fernández Tapias Scientifc Culture 2025-26

HOW ARE THEY FORMED?

• From magma that comes from inside the Earth.

• As the lava cools down, it forms different types of rocks and minerals.

• These rocks are very important

Rapid Cooling

Ascent

Magma Generation

Eruption

Crystallization

What are Volcanic rocks?

• Their crystals are usually very small or not visible at all.

Resistant

Hard

Small crystals

Glassy texture

Porous

CHARACTERISTICS

Very light

Dark colours

light-colours

CLASIFICATION OF VOLCANIC ROCKS

Texture:

• Vesicular (with holes)
• Glassy
• Fine-grained

Chemical composition:

• Acidic (rich in silica)
• Basic (poor in silica)

TWO EXAMPLES

BASALT

• Basalt is the most common volcanic rock on Earth.
• Colour: Dark grey or black

• Texture: Fine-grained

• Composition: Basic (low silica)

• Predominant minerals:

• Pyroxene

• Plagioclase feldspar

• Basalt forms most of the oceanic crust.

Physical properties of basalt

• Density: High (around 3.0 g/cm³)

• Porosity: Low

• Water content: Very low

• Permeability: Low

• Elastic wave velocity: High

• Thermal properties: Good heat resistance

INDUSTRIAL APLICATION

Basalt is widely used as a construction material. Due to its high density and resistance, it is used in road construction, railway ballast and as aggregate in concrete. It is very durable and resistant to weathering.

PUMICE

• Pumice is a very light volcanic rock formed during explosive eruptions.
• Colour: Light grey or white

• Texture: Very vesicular

• Can float on water

• Predominant minerals:

• Volcanic glass

• Feldspar.

Physical properties of pumice

• Density: Very low

• Porosity: Very high

• Water content: Can absorb water

• Permeability: High

• Elastic wave velocity: Low

• Thermal properties: Good thermal insulation

INDUSTRIAL APLICATION

Pumice is mainly used as an abrasive material. Thanks to its high porosity and low density, it is used in cosmetics, cleaning products and stone polishing. It is also used to produce lightweight concrete.

Properties of volcanic minerals

GLOW

COLOURS

Fluorescence/phosphorescence:

Usually dark , but some can be light-coloured

Generally do not show fluorescence or phosphorescence

It dosent't has natural glow

Exfoliation/splitting/ fracture

THE LINE

HARDNESS

HABIT

Crystals are small or poorly developed due to fast cooling

White or light grey

Medium hardness (between 5 and 7)

Cleavage is poor or absent Fracture is usually uneven or conchoidal (in volcanic glass)

TENACITY

RELATIVE DENSITY

Medium to high density (about 2.5 – 3.5 g/cm³)

Brittle

DECEPTION ISLANDS

Geological History

Geography & Nature

• Origins: Formed roughly 10,000 years ago when a massive eruption caused the volcano's summit to collapse.

• Recent Activity: Highly active during the 18th and 19th centuries, with 20th-century eruptions .

• Current Status: Classified as a restless caldera with significant volcanic risk

Location: Situated in the South Shetland Islands, northeast of the Antarctic Peninsula. Unique Structure: An active shield volcano with a distinct horseshoe shape and a 7 km wide sea-filled caldera known as Port Foster. Access: It is one of the only places on Earth where ships can sail directly into the center of a restless volcano via the narrow Neptune’s Bellows channel. .

BIBLIOGRAPHY

https://es.wikipedia.org/wiki/Isla_Decepci%C3%B3n

https://www.geologyin.com/2025/01/volcanic-rocks.html

https://geologiaweb.com/rocas/rocas-volcanicas/

https://thegeotech.com/volcanic-rock-types/

SCIENTIFIC ARTICLE