EXAM 1 Flashcards
The size of the earth’s human population directly affects the severity of many environmental problems. Explain this idea in the context of (a) resources and (b) Pollution.
Resources: Larger human population puts strain on finite resources like freshwater, arable land, and minerals. Overpopulation can lead to overexploitation of resources, depletion of ecosystems, and loss of biodiversity.
Pollution: Higher population densities contribute to increased pollution levels through greater energy consumption, waste generation, and industrial activities. This can lead to air and water pollution, habitat destruction, and climate change.
If Earth’s population exceeds the planet’s carrying capacity, describe three challenges in achieving a comfortable standard of living worldwide?
- Meeting basic needs (food, water, shelter) becomes increasingly difficult.
- Strain on infrastructure and services, leading to inadequate healthcare, education, and sanitation.
- Social tensions and conflicts over dwindling resources and competition for livelihoods.
What is the world’s present population, to the nearest billion? How do the recent population growth rates (over the last few centuries) compare with earlier times? Why?
Present population = 7.9 billion.
Recent population growth rates are higher than earlier times due to factors such as improved healthcare, sanitation, and agricultural practices leading to lower mortality rates
Explain the concept of doubling time. How has the population doubling time been changing through history? What is the approximate doubling time of the world’s population at present?
Doubling time: period it takes for a population to double in size.
Decreasing throughout history due to exponential population growth
Doubling time of the world’s population at present is around 60 years.
What regions of the world currently have the fastest rates of population growth? The Slowest?
Fastest: Sub-Saharan Africa
Slowest: Europe and parts of East Asia
What two properties uniquely define a particular mineral?
Chemical composition
Crystalline structure
What is an igneous rock? How do volcanic and plutonic rocks differ in texture? Why?
Igneous rocks: form from the solidification of molten rock material (magma or lava).
Volcanic rocks: cool quickly at Earth’s surface, fine-grained texture
Plutonic rocks: cool slowly beneath the surface, coarse-grained texture.
How is an igneous rock formed and what mineral group is most common in igneous rocks?
Igneous rocks: form through the crystallization of magma or lava.
Silicate minerals (feldspar, quartz, mica), are most common in igneous rocks.
What is a porphyritic texture and how is it formed?
Porphyritic texture: large crystals (phenocrysts) in fine-grained matrix.
Forms when a magma chamber undergoes a change in cooling rate during crystallization.
What are the two principal groups of sedimentary rocks?
Clastic: formed from the accumulation and cementation of fragments of pre-existing rocks
- Sandstone, shale, conglomerate
Chemical: form from the precipitation of minerals from water solutions
- Limestone, dolostone, rock salt
What are some common physical weathering processes?
Lithification: sediments compact under pressure
Erosion: gradually wearing away
Sedimentation: deposition of sediments
Describe what effects physical weathering might have on chemical weathering
Physical weathering:
- increases surface area of rocks
- Exposes more minerals to chemical weathering agents like water and oxygen
- Creates cracks and fractures,
- Allows penetration of water and chemicals into the rock, speeding up chemical weathering processes.
What is the ‘Principle of Superposition’ and how it is used to determine the relative ages of rocks?
The Principle of Superposition: that in any sequence of undisturbed sedimentary rocks, each layer is older than the one above it and younger than the one below it
Describe how a granite might be transformed into a sedimentary rock.
Granite can be transformed into a sedimentary rock through the process of weathering, erosion, transportation, and deposition of its mineral fragments.
Fragments can accumulate, undergo compaction, and cementation to form a sedimentary rock (arkose, breccia)
What are the possible sources of the heat or pressure that can cause metamorphism?
Magma intrusions
Geothermal gradient (increasing temperature with depth)
Frictional heating during tectonic movements
Pressure for metamorphism can come from the weight of overlying rocks (confining pressure) or tectonic forces (directed pressure).
What is the rock cycle?
Rock cycle: continuous process through which rocks are formed, altered, destroyed, and reformed over geological time scales through various processes (melting, crystallization, weathering, erosion, and metamorphism)
What causes strain in rocks? How do plastic and brittle materials differ in their response to stress?
Strain: caused by the application of stress, resulting in deformation
Plastic: deform permanently under stress (ductile behavior)
Brittle: fracture or deform abruptly under stress (elastic behavior)
What is plate tectonics, and how are continental drift and seafloor spreading related?
Plate tectonics: scientific theory that Earth’s lithosphere is divided into large, rigid plates that move relative to each other
Continental drift: earlier hypothesis proposing that continents were once joined together in a single supercontinent (Pangaea) and have since moved apart
Seafloor spreading: process occurring at mid-ocean ridges where new oceanic crust is formed through volcanic activity and gradually moves away from the ridge
How is paleomagnetic evidence used to support the theory of plate tectonics?
Paleomagnetic evidence: includes the alignment of magnetic minerals in rocks with Earth’s magnetic field at the time of their formation
- Stripes of alternating magnetic polarity parallel to mid-ocean ridges provide evidence for seafloor spreading and plate movement.
- Distribution of earthquakes and volcanoes along plate boundaries
- Matching geological features and rock formations across continents
- Fossil evidence of similar species and ancient climates on different continents that are now widely separated.
Explain how a subduction zone forms and what geologic processes occur at such a plate boundary.
Subduction zone: forms at convergent plate boundaries where one tectonic plate is forced beneath another into the Earth’s mantle
- Oceanic lithosphere (denser) is typically subducted beneath continental lithosphere or another oceanic plate
- Subduction process involves the descent of the subducting plate into the mantle, leading to melting of the descending plate and formation of magma chambers
- Magma can lead to volcanic activity along the overriding plate’s edge
- Intense pressure and heat in the subduction zone can lead to the formation of deep-sea trenches and earthquakes
