Introduction to Geology

Introduction to Geology

• Geology involves studying the solid Earth, terrestrial planets, and moons
• This includes their materials, structures, features, resources, and history
• The findings are applicable in engineering, economy, health, and risk management

Application of Geology

• It helps predict how past events and processes might influence the future
• Understanding these processes aids in avoiding damage to important structures
• Geologists study resources such as oil, natural gas, metals, minerals, ores, rocks, and groundwater
• Many geologists examine past climates and how they have changed

Geology in Everyday Life

• Minerals are components of mobile phones, computers, cables, wind turbines, cars, cosmetics, and batteries
• Groundwater deposits are found hidden in the ground
• Sands, gravels, and crushed stone are used to make concrete for buildings and roads
• Mineral products are part of daily life

History of Earth Science

• Catastrophism (mid 1600s) was based on religious beliefs, like Noah's Flood
• Catastrophism says earth landforms and terrains formed quickly due to sudden events.
• Catastrophism is not widely accepted now
• Uniformitarianism (late 1700s) has the principle "The present is the key to the past"
• James Hutton (1785) suggested that current processes also occurred in the past
• Time is crucial in forming Earth's terrains
• Uniformitarianism is a basic of modern geology

Origin of Earth

• The Nebular Hypothesis explains the formation of the Earth and solar system
• A large rotating nebula of gases and dust existed and shrank, starting its rotation
• Most of the mass, including heavy parts, concentrated in the center, creating the sun and planet nuclei
• The nuclei grew, forming planets, meteorites, and moons

Age of Earth

• Early geologists recognized the great geologic time of Earth but lacked methods to determine the Earth's age
• Radioactivity discovery in the 20th century helped geologists accurately date rocks
• Earth's age is estimated to be about 4.6 billion years
• The universe's age is approximately 14 billion years

Formation of Earth

• Earth is part of a system of planets, moons, and other bodies orbiting the Sun
• The solar system formed simultaneously with the Sun from a cloud of dust, ice, and gases called the Solar Nebula
• The Nebular Hypothesis explains the Sun and planets origin.
• The process starts with a large rotating nebula primarily of hydrogen and helium with other elements

Planetary Composition

• Inner planets (Mercury, Venus, and Mars) have similar structure and composition to Earth
• Giant outer planets (Jupiter, Saturn, Uranus, and Neptune) consist of ice and gas
• Giant outer planets formed in the cooler outer Solar Nebula

Earth's Relation to Universe

• The universe contains moving galaxies
• Galaxies, elliptical and spiral, are conglomerations of stars, dust, and gas
• Solar systems are systems of orbiting planets, asteroids, gases, and ice around the center star (sun)
• Planets include inner planets made of crusts and mantles, outer "gas giants,” and dwarf planets in the Kuiper Belt
• Asteroids contain rock, metals, and ice and comets contain balls of ice and dust

Meteorites Composition

• Meteorites are residues from accretion
• Meteorites age aligns the Earth's age at 4.6 billion years
• They mainly consist of metal, like Earth's core, and Mg Fe silicate minerals, similar to Earth's mantle
• Meteorites chemical composition resembles that of Earth

Earth's Spheres

• Earth consists of interacting spheres: atmosphere, hydrosphere, biosphere (ecosystem), and solid Earth

Atmosphere

• The atmosphere consists of five layers from bottom to top
• Troposphere: the lowest layer, has weather, and cools with height (1°C per 150 meters)
• Stratosphere: contains ozone that absorbs UV radiation, causing temperature to increase upwards
• Mesosphere: the middle layer where meteors burn, reaching colder temperatures upwards; CO2 emits photons
• Thermosphere: temperatures increase upwards potentially reaching 2000 °C and is affected by solar activity
• Exosphere: is the first line of defense against the sun's rays; molecules do not collide, some escape into space
• The atmosphere mainly consists of 75% nitrogen and 25% oxygen
• Nitrogen prevents humans and animals from being poisoned, and prevents oxygen combusting quickly

Hydrosphere

• The hydrosphere includes all forms of water (solid, liquid, gas)
• Earth's water distribution includes more salt water (oceans) than fresh water
• Most fresh water is frozen as glacial
• Unfrozen includes groundwater, surface water, water vapor, and moisture in soil where groundwater is more than surface water

Biosphere

• The biosphere includes all ecosystems: zone of life on earth
• It integrates all living organisms and their relationships and interaction with other elements of the lithosphere, geosphere, hydrosphere, and atmosphere

Geosphere

• The lithosphere (geosphere) encompasses the uppermost mantle and crust
• Uppermost mantle forms the hard outer layer of the Earth where lithosphere is underlain by the asthenosphere

Solid Earth

• Lithosphere has the crust and upper mantle.
• It is mostly silicone and oxygen to make silicates which forms quartz mineral (SiO2).
• It is solid (rigid) and underlined by the asthenosphere.
• Asthenosphere is weak and hot.
• The crust is the Earth's skin in continental and oceanic types
• Mantle is beneath the crust and is primarily viscous liquid cause temperatures are near melting point
• The zone including mountains, volcanoes, deserts, plateaus, and all geological landforms is called the lithosphere

Earth Structure

• Earth consists of: crust, mantle, outer and inner core.
• The core has one third of Earth' mass and consists of iron and nickel in solid inner and liquid outer layers
• Mantle contains over 82% of Earths volume as rocky shell of silicate minerals
• Crust is a thin outer layer, oceanic (3-15 km thick) and continental (10-70 km) thick

Continental vs. Oceanic Crust

• Continental crust is Granite
• Oceanic crust is Basalt
• Continental crust, thicker at (10-70) km, has less density.
• Oceanic crust, thinner at (3-15) km, has more density

Earth's Layers

• The mantle has the biggest volume in Earth's layers
• Mantle triggers earthquakes and volcanoes

Earth's Core

• The core is divided into an outer and inner core
• The outer core is liquid, while the inner core is solid
• The "heaviest mineral" is found in Earth's core and mainly comprises iron and nickel

Geologic Age

• Geologic age is divided into absolute and relative ages
• Absolute age is expressed in numbers
• Relative age compares the age of one object or event to another, like "older" or "younger"

Absolute Age

• The method estimates the age numerically with decaying isotopes
• This method depends on how much the radioactive isotope decay

Isotopes

• Isotopes are element versions with differing neutron counts in the nucleus
• Half-life represents time for radioactive isotope decay into the daughter isotope (half)
• The Parent is the original isotope, and the daughter isotope is the result of decay

Relative Age

• Relative age uses superposition and fossils to determine how old something is
• Superposition: Layers get younger as they rise/go up

Relative Age: Faunal Succession

• Faunal succession (fossils) helps correlate separated areas like the USA, Morocco, UAE, Oman, and Egypt

Relative Age: Cross-Cutting

• Cross-cutting states rocks must be younger rocks cutting across

Rock Layer Expression

• Formation is a rock body with distinct features of significant thickness
• Formations contain rocks of similar rock form and age
• Contact signifies surface separating two formations

Geologic Timelines

• Standard practice to include both

Geologic Timescale

• The geologic timescale ranges downward: EonEraPeriodEraAge
• Parts of the Geologic timescale are broken down because of relative vs absolute ages
• Tectonics, extinctions marks start and end of division

Geological Time Scale Divisions

• The geological time scale has main four divisions.
• Eons followed by eras, periods, and eventually epochs
• 1- Pre-Cambrian Eon represents 80% of Earth's history but with lacking fossils.
• 2- Phanerozoic Eon is 20% of Earth history but the start of plant/animal life

Geologic Time Scale

• Precambrian with vast time (80% of Earth's history) but lacking fossils limited knowledge
• Paleozoic Era ("Old Life") brought complex life and lots of fossils
• Mesozoic Era ("Middle Life") had abundant dinosaurs before their mass extinction
• Cenozoic Era ("New Life") has mammals and birds
• Current period – Cenozoic Era, Quaternary Period, Holocene. Ice also occurred in the Quaternary Period

Human Arrival

• Humans first appeared in the Phanerzoic Eon, Cenozoic Era, Quartnerary Period, Holocene

Event Sequencing

• With the geologic history of an area known, scientists can discover more about events that took place in the past