Geology Exam #2 Flashcards
What is the “norm” on Earth?
Change. There is no static period of earth. It is a dynamic planet with multiple types of change that occurs over different time periods (i.e. plate tectonics, volcanic eruptions, mass movement, etc.)
What makes Earth unique within our solar system?
Temperature range. Earth has liquid water that can only exist from 0-100 degrees celsius. Atmospheric composition (other planets might have toxic air, while we have a non toxic environment with oxygen, carbon dioxide, and nitrogen.)
What are the four “spheres” of Earth?
Lithosphere (rock), hydrosphere (water), biosphere (life, organisms), and atmosphere (air)
What two sources of energy drive interactions among the “spheres”?
The sun (radiant heat) and leftover heat (inner earth).
How old is Earth?
Around 4.5-5 billion years old (at least 4 billion years old).
On this diagram of Earth’s interior, note the properties of the Lithosphere and Asthenosphere, as well as the Crust and Mantle described in class.
The lithosphere is the uppermost layer of the earth. It includes the crust and some other layers. The plates sit in the lithospheric layer. It includes continental/oceanic crust and part of the upper mantle. The Asthenosphere is in between the mantle and lithosphere. This area is warm and shifts the tectonic plates above it.
What is Plate Tectonics?
Everything that happens as it relates to the tectonic plates moving around. The Asthenosphere convects heat and moves the plates above it on the lithosphere. There are convergent plates, divergent plates, and transform boundaries.
What phenomena do plate tectonics help to explain?
Earthquakes (strike-slip, convergent), volcanoes (divergent), mountain building (convergent), pangea. Subduction zones in convergent plate boundaries explain volcanic activity (Ring of Fire) as the denser plate dips below the other plate forming a new crust.
How many major tectonic plates are there on Earth?
8 major tectonic plates.
Where do plates interact?
At plate boundaries
Name/describe the different plate boundary types:
Divergent (spreads apart - mid atlantic ridge) creates new rocks and is usually volcanically active.
Convergent (oceanic intersects with continental) forces subduction and introduces water to rock underground. These zones naturally form magma. There are volcanic eruptions, earthquakes, etc.
Transform (strike-slip) where plates move past one another rigidly. This is often in the South West (California) and sees a lot of earthquakes.
Why do plates move? What causes new crust to form in one place and old crust to be consumed in another place?
As magma moves upwards from the ridges in divergent boundaries, it moves rocks out of the way forcing the plates apart (ridge push). At subduction zones, gravity pulls slabs of rock downwards under other plates. Ridge push and slab pull are the two main driving forces as to why plates move.
How fast do plates typically move?
A few centimeters per year (less than 10. Compared to growth of a fingernail).
What information can geologists get from the rock record preserved in the lithosphere?
Ideas of past climate (temps, water level, atmospheric pressure, etc.), where the sea level was, mass extinction, fossil foils, and more.
What guiding principle do geologists use to interpret the rock record?
Scientific method and the Principle of uniformitarianism (use what we see now to incur what happened in the past.)
Describe the relationship between elements, minerals, and rocks.
Elements are what form minerals, and minerals are discrete known combinations of elements together. Minerals are the building blocks of rocks.
What are the eight most common elements in Earth’s crust, in order?
Oxygen (46.6), Silicon (27.7), Aluminum (8.1), Iron (5.0), Calcium (3.6), Sodium (2.8), Potassium (2.6), Magnesium (2.1).
SIO4 (oxygen and silicon) naturally work together to form most of the rock we see and interact with. Oftentimes, the upper crust of earth is referred to as the silicate earth.
What is the common building block of most rock forming minerals (RFM)?
Oxygen & Sillicon
As we describe the rock cycle in class, make notes on the diagram about the processes and rock types that result from them.
In our rock cycle, rocks are born of magma. When magma hits the surface and cools, it becomes igneous rock. After long periods of weathering from the atmosphere, igneous rock turns into sediment (little pieces of rock transported from the hydrosphere). This sand is deposited along the coastline. These deposits become compacted and lithified to become sedimentary rock, (sandstone). Anywhere through the rock cycle, high temperatures and high pressure can alter rock type. Some metamorphisms cause crystals while others cause foliation (high degree of metamorphism).
Describe each of the following major rock types on Earth–how they are made and their appearance. Give one example of each rock type.
Igneous: magma cooling. Happens quickly (extrusive - magma through volcanic process/rapid motion is quickly brought to the surface and cools giving it no time to form crystals. It is smooth like glass or obsidian) or slow (intrusive - slowly pushed to surface where it forms bigger crystals over a long period of time). Ex: granite, diorite, basalt, etc.
· Sedimentary: unlike igneous, sedimentary rocks are glued together with some material. There are individual layers easily seen. Ex: conglomerate, sandstone, shale, limestone, etc.
· Metamorphic: Harder to distinguish. Foliation or lineations where crystals have aligned into bands. Heated and/or pressured to realign material. Ex: marble, gneiss, schist, metaconglomerate, etc.
Give one example of how part of the rock cycle in the lithosphere is linked to the hydrosphere or atmosphere:
Weathering. Water is the strongest example of this. For example, water slowly breaks down rocks such as limestone. Moving winds carrying sediment also is an example of weathering.
What are some agents of change when it comes to metamorphism of rocks?
Heat/pressure & hydrothermal metamorphism
Where do we find the highest temperatures and pressures related to metamorphism in the crust?
Anywhere near magma there will be high temperatures or pressure around plate boundaries, fault lines, and hotspots (Hawaii). Plate boundaries, divergent boundaries (upwelling magma), and convergent boundaries (creating magma).
Describe the concept of a “biogeochemical cycle”, including flux and reservoirs.
Matter moving around through the spheres of the Earth. Matter can either be accumulated and then it can be stored elsewhere. Flux is how it moves/amount of chemicals moved during these processes over time, and reservoirs is where it collects (crust or oceans).
What are the six most important biogeochemical cycles to life on Earth?
CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur).
Where does the nitrogen in soil come from, naturally?
Nitrogen is naturally in the atmosphere. Trees, plant life, and bacteria use nitrogen through their respective processes and deposit it into the soil where it can be used by even more organisms.
Where does phosphorus in soil come from, naturally? Does it cycle quickly?
Phosphorus comes from decomposers, excretions, etc. It comes from man-made fertilizers too. It does NOT cycle quickly, but it needs to.
Give four examples of natural hazards faced by humans:
Earthquakes, volcanoes, hurricanes, flooding, tornadoes, landslides (mass wastings).
What does it take to cause a natural disaster?
Eruptions and earthquakes commonly cause other natural disasters.
What is the role of science when it comes to natural disasters?
The role of science is to predict and prevent natural disasters as well as mitigate them.
