The Bet of Knowledge≡Magmatic (or igneous) rocks
Magmatic (or igneous) rocks are formed by the cooling and solidification of magma. They are the oldest rocks in the Earth's crust.
Types:
Intrusive (plutonic): They cool slowly inside the Earth, forming large crystals.
Ex.: Granite, diorite.
Extrusive (volcanic): They cool quickly at the surface, with small or non-existent crystals.
E.g.: Basalt, obsidian.
Examples:
Granite: Used in construction.
Basalt: Common in fertile soils (e.g.: terra preta).
Obsidian: Glassy rock used in ornaments.
These rocks are fundamental for geological studies.
Metamorphic rocks
Metamorphic rocks are formed by the transformation of other rocks (igneous, sedimentary or metamorphic) due to high pressure and/or temperature, without melting.
Features:
Foliated texture: Minerals organized in layers (e.g.: gneiss, schist).
Non-foliated texture: No layers, solid appearance (e.g. marble, quartzite).
Examples:
Marble: Originates from limestone.
Quartzite: Derived from sandstone.
Gneiss: Comes from granite.
Shale: Results from mudstones/metapelites.
These rocks are widely used in construction and decoration.
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Discover some interesting facts about Rocks and Minerals
Do you know the Karst relief?? The Amiais stream
Do you know the Karst relief??
The Amiais stream, a small tributary of the Alviela river, is responsible for one of the interesting examples of interaction between water and limestone rock and, Portugal. At a certain point during its journey to the surface, the stream falls and disappears inside the rock through a cave built due to erosion caused by the passage of water over thousands of years.
About the characteristic forms of the karst relief and legend of the figure:
A (Algar)
B (Dolina)
C (Lapiás)
D (Sumidouro)
E (Stalactite)
F (Stalagmite)
G (Cave)
H (Resurgence)
Rocky cliffs and beaches
Rocky cliffs and beaches are common sedimentary landscapes on the Portuguese coast, incessantly shaped by the action of the sea and wind. In several regions of the Atlantic coast in Portugal, the wind is capable of transporting and accumulating sand, resulting in the formation of dunes. Furthermore, rivers carry a large amount of rocky materials that are deposited in their beds and banks, contributing to the formation of river deposits.
The karst model
The karst model is a sedimentary landscape typical of regions dominated by limestone. Rainwater dissolves the limestone, creating cracks that deepen, forming underground wells and caves. The continuous infiltration of water into the limestone promotes its dissolution and feeds the underground watercourses.
The lapiás fields, sinkholes, sinkholes and caves are some geological forms characteristic of the karst model of limestone regions.
The diversity of sedimentary rocks and the geological
The diversity of sedimentary rocks and the geological processes that give rise to them, whether through detrital, chemical or biogenic processes, results in a wide variety of sedimentary landscapes.
A sedimentary landscape is one formed by rocks resulting from the deposition of materials, such as grains or fragments of other rocks, substances dissolved in water or remains of living beings. These rocks are often organized into layers or strata, which are visible in landscapes.
Sedimentary Rocks
Sedimentary rocks are classified based on the origin of the sediments, divided into three groups: Detrital Rocks, formed by the compaction and cementation of fragments of other rocks, such as ballast, sand and clay; Chemiogenic Rocks, originated by the precipitation of substances dissolved in water, such as limestone and rock salt; and Biogenic Rocks, which have biological origin, accumulating remains of living beings or products of their activity, such as coal and conquiferous limestone. Each group represents a distinct training process.
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