Understanding Volcanoes, Earthquakes, and Rock Types
Volcanoes
A volcano is any crack in the earth’s surface that emits incandescent materials from within.
Volcanic Eruptions
Pressure increases in the magma chamber, its walls dilate and fracture, escaping gas and carrying the rest of the magma, similar to what happens when shaking a carbonated drink.
Volcanic Products
- Gases: The first products to reach the surface.
- Lava: The melt.
- Pyroclasts: Solid materials ejected into the air.
- Ashes: The smallest pyroclastic materials.
- Lapilli: Medium-sized pyroclastic materials.
- Blocks: Pyroclastic materials larger than 64mm.
Volcanic Relief
- Crater: A shallow hole in the volcanic cone.
- Volcanic Cone: Made by the accumulation of volcanic materials.
- Fireplace: Conduit connecting the magma chamber with the crater.
- Magma Chamber: Deposit where magma accumulates.
Volcanic Buildings
- Pyroclastic Cone: Small size and steep walls.
- Shield Volcano: A cone with a very broad base.
- Stratovolcano: A cone formed by alternating layers of pyroclastics and lava.
- Dome: A rounded building originating from the output of lava.
Types of Volcanic Activity
The type of volcanic activity depends on gas content, the features of the volcanic building, and lava viscosity.
- Effusive Activity: Kiloulea serves as the model. Characterized by basaltic lava, not accumulated gases, and few pyroclasts.
- Explosive Activity: This eruption can be a model of explosive activity, characterized by viscous lava, accumulated gases, and abundant pyroclastics.
Earthquakes
An earthquake is the vibration of the ground produced by a sharp release of energy. The break occurs when large masses of rock shift. The point where an earthquake originates is called the hypocenter, and the place closest to the hypocenter on the surface is called the epicenter. Its duration is between 20 and 60 seconds.
Tsunamis
The term ‘Tsunami,’ from Japanese, refers to a set of waves of enormous size that suddenly rise, originating in a large body of water at the bottom of the sea. Most tsunamis are caused by earthquakes whose epicenter is located under the sea.
Sedimentary Rocks
Sedimentary rocks are formed from any rock that has undergone a process of erosion, transport, and sedimentation. They are rocks originated as a result of external geological agents.
Sedimentary Detrital Rocks
- Conglomerate: Consisting of large fragments larger than 2 mm.
- Argillite: Consisting of very fine fragments.
- Sandstone: Formed by fragments of average size (<2 mm).
Non-Detrital Sedimentary Rocks
- Plaster: Rock formed by material of the same name.
- Halite: Made by the precipitation of common salt.
- Limestone: Formed by the precipitation of calcium carbonate dissolved in water.
Metamorphic Rocks
Metamorphic rocks form from any rock type by an increase in pressure and temperature. Igneous rocks are also the result of some internal processes, but in this case, the rocks have abandoned their solid state.
- Marble: Has a granoblastic texture, caused by metamorphism of limestone.
- Quartzite: Has a granoblastic texture, originating from metamorphism of sandstone.
Magmatic Rocks
Magmatic rocks are formed by the solidification of magma. These rocks are generated as a result of some internal geological processes, and solidification can occur both on the surface and deep within the Earth.
Volcanic Rocks
- Pumice: A light-colored rock with a vacuolar texture.
- Obsidian: A hard rock with a black and glassy texture.
Plutonic Rocks
- Syenite: Made up mainly of pink feldspar.
- Gabbro: A dark-colored rock composed of feldspar.