GEOL105 Chapter Notes - Chapter 1: Rock Cycle, Scientific Method, Lithification
31 May 2018
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CH 1: Introduction to Natural Hazards
1.1 Why Studying Natural Hazards is Important
● Term process to mean the physical, chemical, and biological ways by which events, like
floods or earthquakes, affect earth’s surface
● Most internal processes are explained by the theory of plate tectonics
○ Tectonic plates: large surface blocks of the solid earth
○ Mapped by identifying zones of earthquakes and active volcanism
● Internal processes done by internal forces deep in the earth
● External forces are near or on earth’s surface
● The energy released by natural processes varies greatly
● Often use the terms hazard, disaster, and catastrophe to describe our interaction with
natural processes
● Natural hazard: a natural process and event that is a potential threat to human life and
property
● Disaster: a hazardous event that occurs over a limited time span within a defined area
○ 10 or more people killed
○ 100 or more people are affected
○ A state of emergency is declared
○ International assistance is requested
● Catastrophe: a massive disaster that requires significant expenditure of money and a
long time (often years) for recovery to take place
● On average, 80000 people die each year from natural disasters
● Financial loss now exceeds $50 billion per year
● Impact of events is directly connected to human population density and land use
patterns
● During 1990s, a record number of great catastrophes occurred worldwide
● During the past half century, there has been a dramatic increase in natural disasters
○ Flooding and storms are the major cause of fatalities
○ Countries with medium to low income suffered the most from floods and storms
○ Medium-income countries suffer the greatest losesses, with over 90% of all
deaths and about 40% of the total economic losses
○ High-income countries suffered the greatest economic losses but the lowest
number of deaths
● Mitigation: to reduce the effects of something
○ Often used by scientists, planners, and policy makers in describing disaster
preparedness efforts
● An important aspect of all natural hazards is their potential to produce a catastrophe
○ High potential: floods, hurricanes, tornadoes, earthquakes, volcanic eruptions,
large wildfires, heat waves
○ Moderate potential: landslides, droughts
○ Low potential: coastal erosion, frost, lightning, expansive soils
1.2 Role of History in Understanding Hazards
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● Natural hazards are repetitive events, the study of their history provides much-needed
info for any hazard reduction plan
● Study its historic occurence and any geologic features that it may produce or affect
○ Features may be landforms, such as channel, hills, or beaches; structures, such
as geologic faults, cracks, or folded rock; or earth materials, such as lava flows,
meteorites, or soil
● “Read the landscape”
1.3 The Geologic Cycle
● Geologic cycle: a group of interrelated sequences of earth processes known as the
hydrologic, rock, tectonic, and biogeochemical cycles
● Geologic conditions and materials largely govern the type, location, and intensity of
natural processes
● The Tectonic Cycle
○ The term tectonic refers to the large-scale geologic processes that deform
earth’s crust and produce landforms such as ocean basins, continents, and
mountains
○ Tectonic processes are driven by forces deep within the earth
○ To describe these processes, we use info about the composition and layering of
earth’s interior and about the large blocks of the solid earth we call tectonic
plates
○ Tectonic cycle: a repetitive sequence of events and processes that create and
destroy the earth’s crust and its ocean basins and mountain ranges
○ Responsible for the production and distribution of rock and mineral resources
invaluable to modern civilization and hazards such as volcanoes and
earthquakes
● The Rock Cycle
○ Rock cycle: group of interrelated processes by which igneous, metamorphic,
and sedimentary rocks can each be produced from the others
■ Igneous: an aggregate of minerals formed from the solidification or
explosion of magma; extrusive if it crystallized on or very near the surface
of earth, intrusive if it crystallized well beneath the surface
■ Sedimentary: hard, compacted, and cemented particulate material that
was created by weathering, biological activity, or chemical precipitation
● Lithification: conversion to solid rock, takes place by cementation
and compaction as sediment is buried beneath other sediment
■ Metamorphic: an aggregate of minerals that formed beneath the earth’s
surface from preexisting rock by the effects of heat, pressure, and
chemically active fluids
● In foliated, mineral grains are preferentially aligned parallel to one
another or light and dark minerals are segregated into bands
● Nonfoliated have neither characteristic
○ Rocks are aggregates of one or minerals
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Term process to mean the physical, chemical, and biological ways by which events, like floods or earthquakes, affect earth"s surface. Most internal processes are explained by the theory of plate tectonics. Tectonic plates: large surface blocks of the solid earth. Mapped by identifying zones of earthquakes and active volcanism. Internal processes done by internal forces deep in the earth. External forces are near or on earth"s surface. The energy released by natural processes varies greatly. Often use the terms hazard, disaster, and catastrophe to describe our interaction with natural processes. Natural hazard: a natural process and event that is a potential threat to human life and property. Disaster: a hazardous event that occurs over a limited time span within a defined area. Catastrophe: a massive disaster that requires significant expenditure of money and a long time (often years) for recovery to take place. On average, 80000 people die each year from natural disasters.
