Notes, summaries, assignments, exams, and problems for Geology

Plastics

Plastics are materials composed of polymers, consisting of long chains of atoms that contain carbon.

Types of Plastics

• Natural Plastics: Directly obtained from vegetable raw materials (cellulose and cellophane, latex) or animal (casein).
• Synthetic or Artificial Plastics: Made from compounds derived from petroleum, natural gas, or coal.

Industrial processing of these raw materials and compounds is called polymerization.

During the production of plastics, fillers are added (materials such as glass fiber, textile fibers, silica, paper, filler, or sawdust). Some additives (chemicals) are also incorporated.

As we have seen, properties such as elasticity, rigidity, toughness, and flexibility are specific to certain plastics.

Most plastics are not... Continue reading "Types of Plastics, Fibers, and Construction Materials" »

Urban Planning Models

Ensanche - The Hippodamic Model

Early models for expanding cities with old layouts proposed a Hippodamic growth system. In Spain, this model was used in Madrid's widening plan and in Barcelona with Cerdà's plan.

Cerdà's Plan

Cerdà's plan proposed a smaller grid than the original Hippodamic model, with a hierarchy of roads. Over time, this evolved into the Salamanca district, which became obsolete. The urban development was regulated by legislation, including the types of buildings allowed in each block, establishing a social organization among buildings.

The approach was to create courtyards within blocks. Due to their small size, these courtyards were primarily for ventilation and suffered from scale issues over time. The... Continue reading "Urban Planning Models: Ensanche & Linear City" »

Sierra de Perija

Location: The Sierra de Perija begins in the middle of the river valley and extends slightly north of 11 degrees latitude, where the Oca mountains transition into the Guajira Peninsula lowlands.

Constitution and Relief

Predominantly composed of igneous and metamorphic rocks (Precambrian, Cenozoic), the area is difficult to access and settle due to the absence of alluvial valleys and terraces. The altitude reaches approximately 4000 meters, with peaks exceeding 3750 meters at Tetaria. Key sectors include the Motilones range, Valledepur, Sierra de Perija, and Goose mountains.

Vegetation, Climate, and Hydrography

The landscape features abundant forest vegetation, especially at higher elevations, due to high rainfall. The high mountains... Continue reading "Geographic Formations: Sierra de Perija, Lara-Falcón, Barquisimeto" »

Earth's Layers and Composition

Core

The Earth's core, a zone of higher density and temperature, occupies 17% of the Earth's volume. The inner core is denser than the outer core.

Mantle

The mantle, with a thickness of 2900 km, occupies 82% of the Earth's volume. It has a lower density than the core. Convection currents in the asthenosphere, a part of the upper mantle, drive the movement of tectonic plates in the lithosphere.

Lithosphere

The lithosphere, the outermost layer, is less dense and colder than the mantle. It forms the oceanic and continental crust. The main constituents of the crust are rocks, which are solid, natural aggregates of one or more minerals.

Tectonic Plate Movement and its Effects

Tectonic plates move at a very slow velocity. The... Continue reading "Earth's Structure and Dynamic Processes: A Comprehensive Overview" »

Fabrication Painting: Cleaning and Degreasing

The areas of the car body tend to accumulate fat and dust, which must be removed before painting to ensure the product's adherence to the wing area.

Phosphating

This is a surface treatment that converts the metal. The metal is treated with a layer of microcrystalline zinc phosphate. The bodywork is immersed in a bath of composite with phosphoric acid, zinc phosphate additives, and accelerators. This provides a more uniform coating and better penetration into the hollow parts than spraying.

Responsibilities

After the phosphating process, the surface is washed with a passivating aqueous solution, which improves grip and anticorrosion protection.

Drying

This is performed with hot air to harden the layers... Continue reading "Automotive Body Painting: Processes and Techniques" »

Earth's Formation and Geological History

How Earth Formed (Approx. 4600 Mya)

Earth was formed approximately 4,600 million years ago. It originated from a gas and dust nebula. Following a stellar explosion (supernova), this gas and dust contracted and condensed to form our planet.

Geological Time Scale (Millions of Years Ago - Mya)

• Archean Eon: 4600 - 2500 Mya
• Proterozoic Eon: 2500 - 541 Mya
• Paleozoic Era:
  • Cambrian Period: 541 - 485 Mya
  • Ordovician Period: 485 - 444 Mya
  • Silurian Period: 444 - 419 Mya
  • Devonian Period: 419 - 359 Mya
  • Carboniferous Period: 359 - 299 Mya
  • Permian Period: 299 - 252 Mya
• Mesozoic Era:
  • Triassic Period: 252 - 201 Mya
  • Jurassic Period: 201 - 145 Mya
  • Cretaceous Period: 145 - 66 Mya
• Cenozoic Era:
  • Tertiary Period (Paleogene & Neogene): 66

The Galaico-Leonese Massif

The northwest corner of the Meseta Central, the Galaico-Leonese Massif, fractured and rejuvenated during the Alpine orogeny. It consists of Paleozoic materials and features rounded, low-lying mountains cut by faults. Its most prominent mountains are Segundera, Cabrera, and Ancares.

The Cantabrian Mountains

The Cantabrian Mountains have two sectors:

• The Asturian Massif: Composed of Paleozoic materials that were part of the Meseta Central and rejuvenated in the Alpine orogeny. Its western end features varying hardness of materials (slates and quartzites), while its eastern end consists of limestone.
• The eastern Cantabrian Mountains: Composed of Mesozoic limestone materials deposited by the sea and folded during the Alpine

Origin of Life on Earth

The early ocean contained organic molecules: lipids, amino acids, carbohydrates, forming an organic soup. Coacervates formed, which were (proto) lipid droplets surrounded by RNA. These coacervates acquired the ability to nurture and make copies of themselves, therefore forming the first simple cells: prokaryotes and heterotrophic cells that were already anaerobic. These cells contained RNA.

Many cells died from lack of food, and others, through mutation, were able to make their own food with H₂O + CO₂ and energy from the sun. These were autotrophic prokaryotic cells. They produced oxygen, which combined with other elements over the course of nature. The ozone layer formed, protecting living things from ultraviolet radiation.... Continue reading "Earth's Formation and Dynamic Processes" »

Water Contaminants

Water pollution can have natural or human origins. Contaminants can be physical (suspended solids), chemical (organic matter, nitrogen compounds, heavy metals), or biological (bacteria, viruses, protozoa, parasitic worms). Effects: Birds cannot fly due to oil ingress, fish stocks decrease, and coastal ecosystems are affected. Consequences:

• Eutrophication: Proliferation of photosynthetic organisms in water bodies.
• Water Temperature Increase: Hot water mixes with cold water and contaminates it.
• Salinization of Aquifers: Salty ocean water mixes with fresh groundwater.

Water Purification

Drinking water should be odorless, colorless, and tasteless, and it should contain no toxic substances. Water undergoes chemical processes to remove... Continue reading "Water Contamination, Purification, and Biodiversity Conservation" »

Steel Heat Treatments

Standardizing (Normalizing)

Steels often exhibit plastic deformation; for example, they might have a pearlitic structure with relatively irregular grain sizes. A standard thermal treatment, known as normalizing, is applied to refine the steel and achieve a uniform grain distribution. Normalizing involves heating the material to a temperature between 55°C and 85°C above the upper critical temperature, followed by relatively fast cooling in air.

Annealing

This procedure is applied to low and medium-carbon steels that have been machined or significantly deformed through cold forming. The alloy is heated to austenitize it, typically 15°C to 40°C above the critical temperature. It is then allowed to cool slowly inside the furnace,... Continue reading "Steel Heat Treatments and Corrosion Mechanisms" »