chapter 1 understanding earth: a dynamic and evolving planet
TRANSCRIPT
CHAPTER 1Understanding Earth:
A Dynamic and Evolving Planet
Introduction
Geology is a complex, integrated system of related parts, components, or sub-systems.
These interact in an organized fashion, affecting one another in various ways. The principal subsystems of the earth are the:
Atmosphere Biosphere Hydrosphere Lithosphere Mantle Core Figure 1.1, p. 5
Organisms break down rockinto soil. People alter thelandscape. Plate movementaffects evolution anddistribution of Earth’s biota.
Plate movement affects size,shape, and distribution ofocean basins. Running waterand glaciers erode rock andsculpt landscapes.
Hydrosphere Biosphere
Fig. 1-1, p. 5
Evaporation, condensation,and precipitation transferwater between atmosphereand hydrosphere, influencingweather and climate anddistribution of water.
Plant, animal, and humanactivity affect composition ofatmospheric gases.Atmospheric temperature andprecipitation help to determinedistribution of Earth’s biota.
Atmosphere
Atmospheric gases andprecipitation contribute toweathering of rocks.
Plants absorb and transpire water.Water is used by people for domestic,agricultural, and industrial uses.
Water helps determine abundance,diversity, and distribution oforganisms.
Heat reflected from land surface affectstemperature of atmosphere. Distributionof mountains affects weather patterns.
Convection cells within mantle contribute to movement of plates (lithosphere) and recycling of lithospheric material.
CoreSupplies heatfor convection
in mantle
Mantle
Plate
What is Geology?
Geology is the study of the Earth, other planets and their moons.
Physical geology is concerned with the materials and processes which compose and operate on the surface of, and within, Earth.
Historical geology is concerned with the origin and evolution of Earth's continents, oceans, atmosphere, and life.
What is geology?
Geologists are employed in diverse occupations.
Principle occupations include:
Mineral and energy resource exploration Solving environmental problems Predicting natural disasters
Geology and the Formulation of Theories
What is a theory?
Derived from the scientific method, which involves:
gathering and analyzing facts formulating hypotheses to explain the
phenomenon testing the hypotheses and finally proposing a theory.
Science makes no claim about the existence or nonexistence of the supernatural.
Geology and the Formulation of Theories
In science, a theory is NOT a hunch or guess, but a reliable
explanation supported by a large amount of evidence.
In geology, plate tectonics is an important theory.
Geology and the Formulation of Theories
What is a theory?
The hypotheses is a tentative explanation.
A scientific theory is a testable explanation for some natural phenomenon, that is supported by a large body of evidence.
How Does Geology Relate to the Human Experience?
Geology pervades our everyday lives and is a part of many aspects of human experience, including the arts and literature.
The range of environmental problems, resources, military tactics, and other issues of concern to society require a basic understanding of geology.
Figure 1.2, p. 6
How does geology affect our daily lives?
Natural Disasters Economics and Politics Our Role as Decision
Makers Consumers and
Citizens Sustainable
Development
Figure 1.3, p. 7
Fig. 1-3, p. 7
629 kgCopper
9203 kgClays
774,000 kgStone, sand,and gravel
311,034 lPetroleum
348 kgZinc
14,359 kgSalt
410 kgLead
>30,615 kgOther minerals
and metals
159,880 m3
Natural gas
14,694 kgIron ore
33,771 kgCement
2438 kgBauxite
(Aluminum)
260,530 kgCoal
8301 kgPhosphate rock44 g
GoldStepped Art
Global Geologic and Environmental Issues Facing Humankind
Most scientists would argue that overpopulation is the greatest problem facing the world today.
7 billion in 2011, perhaps 9 billion by 2045.
Increasingly large numbers of people must be fed, housed, and clothed, with a minimal impact on the environment.
Global Geologic and Environmental Issues Facing Humankind
Problems associated with overpopulation
Increased risks from earthquakes, tsunami, floods and volcanoes
More pollution Wildlife threatened Shortages of resources Poverty
Global Geologic and Environmental Issues Facing Humankind
Greenhouse effect: Retention of heat in the atmosphere.
Humanity has been adding to the greenhouse. This results in an increase in the temperature of
Earth’s surface and atmosphere, thus producing global warming.
Figure 1.4, p. 8
Fig. 1-4, p. 8
Stepped Art
a) Short-wavelength radiation from the Sun that is not reflected back into space penetrates the atmosphere and warms Earth’s surface.
b) Earth’s surface radiates heat in the form of long–wavelength radiation back into the atmosphere, where some of it escapes into space. The rest is absorbed by greenhouse gases and water vapor and reradiated back toward Earth.
c) Increased concentrations of greenhouse gases trap more heat near Earth’s surface, causing a general increase in surface and atmospherictemperatures, which leads to global warming.
Greenhouse Effect
Origin of the Universe
Did it begin with a Big Bang?
In the Big Bang theory, the universe began approximately 14 billion years ago.
An extremely dense, hot body of matter expanded and cooled
Origin of the Universe
How do we know? Evidence for the Big Bang:
the universe is expanding from a central point.
The entire universe has a pervasive and constant background radiation, thought to be the faint afterglow of the Big Bang.Fig. 1.7, p.
10
Origin of the Universe
Evidence for the Big Bang: Expansion of the Universe
Objects farther from the Earth are moving faster away from us.
Confirmed with the Doppler Effect.
Fig. 1.6, p. 10
Our Solar System
Sun: a star 8 planets (Pluto no longer considered a planet) Numerous moons, asteroids and comets About 4.6 billion years old
Figure 1.8, p. 11
Our Solar System: Its Origin and Evolution
Formed from a rotating cloud (nebula) of matter about 4.6 billion years ago.
The cloud condensed, collapsed from gravity and flattened into a rotating disk.
The Sun, planets, and moons formed within this disk.
Figure 1.9, p. 12
Earth: Its Place in Our Solar System
Earth condensed as a solid body from the solar nebula about 4.6 billion years ago.
Soon after internal heat differentiated the Earth into a layered planet.
Fig. 1.10, p. 13
Why Earth is a Dynamic and Evolving Planet
Earth has continuously changed during its 4.6 billion year existence as a result of interactions between its various subsystems and cycles.
As the earth differentiated, 3 concentric layers formed.
Crust Mantle Core.
Why Earth is a Dynamic andEvolving Planet
Fig. 1.11, p. 13
The core consists of
a small, solid inner region
a larger, liquid, outer portion
Composed of iron and a small amount of nickel.
The Core
Why Earth is a Dynamic and Evolving Planet
Fig. 1.11, p. 13
Why Earth is a Dynamic and Evolving Planet
The mantle surrounds the core and is divided into:
a solid lower mantle
a partially molten asthenosphere that overall behaves plastically and flows slowly
a solid upper mantle.
Composed primarily of peridotite, an igneous rock made of olivine.
The Mantle
Fig. 1-11, p. 13
Why Earth is a Dynamic and Evolving Planet
The outermost layer, the crust, is divided into:
thick continental crust
thin oceanic crust
The Crust
Fig. 1.11, p. 13
Why Earth is a Dynamic and Evolving Planet
The Asthenosphere
Surrounds the lower mantle Behaves plastically and
slowly flows Partial melting in the
asthenosphere generates magma (molten rock) that rises to the earth’s surface.
Fig. 1.11, p. 13
Why Earth is a Dynamic and Evolving Planet
The Lithosphere
The crust and upper mantle make up the lithosphere which forms the solid outer layers of the Earth.
Fig. 1.11, p. 13
Why Earth is a Dynamic and Evolving Planet
Plate Tectonic Theory The lithosphere is composed of rigid plates
that diverge, converge, or slide sideways past one another as they move over the asthenosphere
Fig. 1.12, p. 16
Fig. 1-12, p. 16
Convectioncell
Innercore
Mantle
Outercore
Upwelling Hot
Cold
Continentallithosphere
Trench
Mid-oceanic ridge
Ocean
Subduction
Oceaniclithosphere
Stepped Art
Why Earth is a Dynamic and Evolving Planet
Plate Tectonic Theory: The Plates
Fig. 1.13, p. 16
Why Earth is a Dynamic and Evolving Planet
Plate Tectonic Theory: Boundaries between Plates
Volcanoes and earthquakes occur at the boundaries between the plates. Fig. 1.14,
p. 17
Why Earth is a Dynamic and Evolving Planet
Plate Tectonics and Earth Systems
Plate tectonic theory is a unifying explanation for many geologic features and events, helping us understand the composition and internal processes of Earth on a global scale.
The Rock Cycle
A rock is a solid aggregate of one or more minerals, as well as non-crystalline matter such as natural glass or organic material like coal.
Fig. 1.15, p. 18
Three major groups of rocks: Igneous Sedimentary Metamorphic
The Rock Cycle Igneous Rocks form from the crystallization of
cooling magma or the consolidation of volcanic ejecta. Intrusive igneous rock
crystallizes beneath the Earth’s surface.
Extrusive igneous rock crystallizes and cools at the earth’s surface. At times it cools so fast that it forms a glass or ash.
GraniteIntrusive Igneous Rock
BasaltExtrusive Igneous Rock Fig. 1.16 a-b,
p. 19
The Rock Cycle
Sedimentary Rocks typically layered deposits formed from:
rock/mineral fragments precipitation of minerals from solution the compaction of plant and animal remains.
LimestonePrecipitation from seawater
ConglomerateForms from river gravels
Fig. 1.16 c-d, p. 19
The Rock Cycle Metamorphic Rocks form from alteration of
other rocks, usually by: Heat Pressure Chemically active fluids
Gneiss
Fig. 1.19 e-f, p. 19
Quartzite
The Rock Cycle
The rock cycle illustrates the interactions between Earth’s internal and external processes and how the three rock groups are interrelated.
Fig. 1.15, p. 18
The Rock Cycle
How are the rock cycle and plate tectonics related?
Plate movement is the driving mechanism of the rock cycle. Plate interaction determines, to some extent, which of the three rock groups will form.
Fig. 1.17, p. 20
Organic Evolution and the History of Life
The theory of organic evolution states:
that all living things are related have descended with modification from
organisms living in the past.
Charles Darwin proposed that the mechanism of natural selection results in survival to reproductive age of organisms best suited to their environment.
Fossils, the remains of once-living organisms provide evidence for evolution and a history of life before humans.
Organic Evolution and Plate Tectonics
Together the theories of plate tectonics and organic evolution have changed the way we view
our planet.
Geologic Time
An appreciation of the immensity of geologic time is central to understanding the evolution of the Earth and its life.
Earth goes through cycles of much longer duration than the human perspective of time
The geologic time scale is the calendar that geologists use to date past events in Earth’s history.
Fig. 1.18, p. 22
Geologic Time
Fig. 1.18, p. 22
Geologic Time and Uniformitarianism
Uniformitarianism forms a cornerstone of geology. It is a fundamental tenet of geology.
This principle states that the laws of nature have remained unchanged through time and thus, that the processes observed today have also operated in the past, though possibly at different rates.
Therefore, to understand and interpret geologic events from evidence preserved in rocks, geologists must first understand present-day processes in rocks.
How does the study ofgeology benefit us?
Understanding how the Earth’s subsystems work will help ensure the survival of the human species.
It will help us to understand how our actions affect the delicate balance between these systems.
End of Chapter 1