Geology Test 1
What are the important features of convergent plate boundaries?
- two plates move toward each other and the leading edge of one is bent downward as it slides beneath the other. -island arches, mountains, volcanoes created
What are the important features of divergent plate boundaries?
-located along the crests of oceanic ridges - two adjacent plates move away from each other - create new plates (lithosphere is created)
What are the important features of transform plate boundaries?
-plates slide horizontally past one another without the production or destruction of lithosphere - found on the ocean floor mostly -creates earthquakes and faults
What are the 3 causes of melting and what tectonic environment are they associated with?
1. Decompression melting 2. addition of water 3. Temperature increase
What is the supporting evidence of continental drift?
1. Fit of the continents 2. Fossils matching across oceans 3. Matching geological units across oceans 4. Paleoclimate: locations of past glaciations and tropical swamps
How are minerals classified?
1. Naturally occurring 2. Generally inorganic 3. Solid Substance 4. Orderly crystalline structure 5. definite chemical composition that allows for some variation
Consider Bowen's reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt? A) olivine B) quartz C) orthoclase D) sodium-rich plagioclase
A
Partial melting results in a magma that is nearer the ________ end of the compositional spectrum than the parent rock from which it was derived. A) felsic B) ultramafic C) mafic D) basaltic
A
The Aleutian Islands occur at a ________. A) convergent boundary on a volcanic arc above a northward-subducting Pacific plate B) transform boundary where North America has moved towards Alaska C) divergent boundary where shield volcanoes are forming D) convergent, continental margin with uplifted fault blocks, much like those of the Basin and Range Province
A
The main reason for the elevated position of the oceanic ridge is because ________. A) it is hot, and therefore less dense than the cooler rocks surrounding it B) it is the result of the collision of two tectonic plates, which pushes up the ridge C) oceanic crust is less dense than continental crust D) as one oceanic plate is submerged beneath another, the ridge is pushed up
A
________ reacts readily with acids such as hydrochloric. A) Calcite B) Quartz C) Diamond D) Talc
A
What is an anion?
A negatively charged ion
Who proposed continental drift?
Alfred Wegener
How does igneous rock formation correlate with plate tectonics?
At diverging plate boundaries, convection currents bring hot magma to the surface. This hot magma flows out onto the ocean floor, forming extrusive, finely grained igneous rocks. At convergent plate boundaries, sedimentary rock from the ocean floor gets pushed down into the mantle.
Each atom of the same element, zinc for example, has the same number of ________. A) electrons in the nucleus B) protons in the nucleus C) neutrons in the outer nuclear shell D) electrons in the valence bond level
B
How do the electrons behave in a mineral with metallic bonding? A) They are tightly bound to certain atoms and cannot readily move. B) They can move relatively easily from atom to atom inside the mineral. C) They react with protons to make neutrons in the outer valence shells. D) They move to adjacent negative ions, forming positive ions.
B
Mount St. Helens is ________. A) a basaltic cinder cone B) an explosive stratovolcano C) a basaltic shield volcano D) a small, welded tuff cone
B
When magma cools too fast for mineral grains to grow, the resultant texture is called ________. A) porphyritic B) glassy C) vesicular D) pyroclastic
B
Which one of the following is NOT true for minerals? A) They have a specific, internal, crystalline structure. B) They can be a liquid, solid, or gas. C) They have a specific, predictable chemical composition. D) They can be identified by characteristic physical properties.
B
Which type of plate boundary occurs where two plates move apart, resulting in upwelling and partial melting of hot material from the mantle? A) convergent boundary B) divergent boundary C) transform boundary D) transition boundary
B
________ is often paraphrased as "the present is the key to the past." A) Historical geology B) Uniformitarianism C) Aristotelian logic D) Catastrophism
B
________ is the name given to molten rock when it reaches Earth's surface. A) Magma B) Lava C) Igneous D) Melt
B
________ was never proposed as evidence supporting the existence of Pangaea. A) Geometrical fit between South America and Africa B) Islands of Precambrian rocks along the Mid-Atlantic Ridge C) Late Paleozoic glacial features D) Similar fossils on different continents
B
Cinder Cones
Basalt, lesser andesite, fragmental, small, steep slope, form quickly, large craters (calderas)
Examine the words and/or phrases below and determine the relationship among the majority of words/phrases. Choose the option that does not fit the pattern. A) oceanic ridge B) seafloor spreading C) arc volcanoes D) divergent
C
In the early part of the twentieth century, ________ argued forcefully for continental drift. A) Karl Wagner B) Peter Rommel C) Alfred Wegener D) Bill Kohl
C
The Icelandic volcanoes are related to plate tectonics because ________. A) they lie on a spreading center where two plates are converging B) they lie on a subduction zone where two plates are converging C) they lie on a spreading center where two plates are moving apart D) they lie along a subduction zone where two plates are diverging
C
The ________ Ocean Basin is rimmed by the most subduction zones. A) Atlantic B) Indian C) Pacific D) Arctic
C
The currently accepted age of the Earth is ________ years. A) 4.6 thousand B) 6.4 trillion C) 4.6 billion D) 6.4 million
C
The subduction of cold, dense oceanic lithosphere-a major driving force of plate motion-is known as ________. A) convection B) ridge push C) slab pull D) convective flow
C
Which of the following is an Earth layer defined based on its chemical composition? A) asthenosphere B) lithosphere C) crust D) transition zone
C
Which of the following is most likely to result in an effusive eruption? A) magma with a high silica composition B) highly viscous magma C) magma with a low silica composition D) rhyolitic magma
C
Which of the following minerals is a ferromagnesian silicate? A) quartz B) orthoclase C) hornblende D) muscovite
C
what kinds of volcanic activity and volcanic landforms to you observe at hot spots?
Cinder Cones
What is the lithosphere?
Consists of the entire crust plus the uppermost mantle. Forms Earth's relatively cool, rigid outer shell. 100 km thick
Name one continental and one oceanic hotspot in the U.S.
Continental- Yellowstone Oceanic- Hawaii
What drives plate tectonics?
Convection: mantle heats up and rises, melts and as it cools it creates rocks and spreads out
Where do volcanoes occur?
Convergent Boundaries, Divergent Boundaries, & Hot Spots occurs where magma rises through the earths crust and reaches the surface.
A ________ is a well-tested and widely accepted view that best explains certain scientific observations. A) hypothesis B) generalization C) law D) theory
D
A ________ volcano is a very large, gently sloping mound composed mainly of basaltic lava flows. A) composite B) stratospheric C) cinder cone D) shield
D
A very long-lived magma source located deep in the mantle is called a ________. A) magma welt B) basalt spout C) melt well D) hot spot
D
All silicate minerals contain ________ and ________. A) iron; silicon B) silicon; sodium C) oxygen; carbon D) silicon; oxygen
D
Examine the words and/or phrases below and determine the relationship among the majority of words/phrases. Choose the option that does not fit the pattern. A) quartz B) mica C) feldspar D) calcite
D
In a porphyritic volcanic rock, which mineral grains are the last to crystallize? A) phenocrysts B) vesicles C) pegmatites D) matrix or groundmass
D
The asthenosphere ________. A) is a subdivision of the outer core B) is a zone of strong material near the inner core C) contains Earth's crust and upper mantle D) is a relatively weak zone within the mantle
D
Which of the following is an accurate description of ionic bonding? A) Nuclei of bonding atoms exchange electrons; the resulting ions are bonded together by the attractive forces between the negative and positive nucleons. B) Atoms of two different elements share electrons and protons; the resulting compound is bonded together by the strong, binding energy of shared protons. C) Nuclei of two different atoms share electrons, and the resulting compound is tightly bonded by the very strong, induced, electronuclear bonds. D) Atoms of different elements, having gained or lost electrons, form negative and positive ions that are bonded together by attractive forces between ions with opposite charges.
D
Which of the following statements about pyroclastic flows is TRUE? A) They commonly occur as part of basaltic volcanism at midocean ridges. B) They are comprised of water-saturated volcanic debris that builds up from repeated eruptions. C) They are slow-moving, but because of their high temperature they are quite deadly. D) They consist of hot gasses infused with ash and lava fragments and move at extremely high speed.
D
________ has the same mineral composition as andesite. A) Basalt B) Granite C) Gabbro D) Diorite
D
________ rocks are composed almost entirely of light-colored silicates. A) Ultramafic B) Basaltic C) Mafic D) Felsic
D
Development of Theories
Explanations of the relationship between scientific facts that have been independently tested and not (yet) invalidated.
What minerals characterize intermediate rocks?
In- Diorite Ex- Adesite
What minerals characterize ultramafic rocks?
In- pendotite
What history does a glassy rock indicate?
Indicates that magma cooled extremely fast, so no crystals could form.
Why are magnetic reversals important in understanding plate tectonics?
It is used to determine the magnetic history of Earth, volcanoes, and seafloor spreading.
What are hotspots?
Long, vertical columns of hot magma - occur either under oceanic or continental crusts - creates volcanos
Why is paleomagnetism important for understanding continental drift and plate tectonics?
Magnetism in rocks and polar wandering, and magnetic anomalities, helps to understand
what kinds of volcanic activity and volcanic landforms to you observe at divergent boundaries?
Mid ocean ridges and rift valleys
Why aren't there very old rocks in the oceans compared to the continents?
Ocean rocks are denser than continental rocks, so when these rocks collide, ocean rocks subdue under the continental rocks, causing new ones to form in their places.
What are the differences between the oceanic and continental crusts?
Oceanic- 7 km thick, composed of dark igneous rock: basalt. Continental- 35 km thick, consists of many rock types, mainly granodiorite.
What are the major hazards associated with volcanic eruptions?
Pyroclastic Flows: hot gases infused with ash and other debris Lahars: type of mudflow generated by volcanic eruptions Calderas: steep walled depression that is larger than 1 km Tsunamis
What minerals characterize felsic rocks
Rich in silicate minerals, magma and rocks that are enriched in the lighter elements such as silicon, oxygen aluminum, sodium and potassium In- granite ex- rhyolite
what kinds of volcanic activity and volcanic landforms to you observe at convergent boundaries?
Ring of fire
The Nature of Scientific Inquiry
Science assumes the natural world is consistent and predictable
What does Bowen's reaction series show?
Shows how magma's minerals change as the magma cools
Construction of a Hypothesis
Testable explanations of the relationship between scientific facts can be relatively simple and preliminary
What is the Moho?
The boundary between the crust and mantle. The depth varies from 3 miles beneath the ocean floor to 25 miles beneath the continents.
What is Bowen's reaction series?
The discontinuous series starts with olivine, then pyroxene, amphibole, then biotite.
How is the classification of the asthenosphere and the lithosphere different from the core, mantle and crust?
The lithosphere and asthenosphere are classified physically, while the core, mantle and crust are chemically classified.
What is sea floor spreading?
The process by which molten material adds new oceanic crust to the ocean floor. axis of mid-ocean ridge extends out laterally in both directions.
How do we subdivide this class of minerals?
The silicate class is subdivided by their structure - tetrahedra - double tetrahedra - rings - single chain - double chain -sheets
How does grain size of an igneous rock vary with cooling rate?
The slower the cooling rate, the larger the grain size. The faster the cooling rate, the smaller the grain size.
What is paleomagnetism?
The study of the record of Earth's magnetic field in rocks.
How do ionic bonds work?
Through the loss or gain of electron from ions to form a stable compound - electron transfer
What factors affect the eruptive style of a volcano?
Viscosity, gas content
Why wasn't continental drift immediately accepted?
Wegner lacked mechanisms to explain how continents could move. Hypothesis couldn't be tested until 30 years later with the discovery of paleomagnetism.
What is the scientific method?
a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.
What is a cation?
a positively charged ion
What are minerals?
building blocks of rocks - solid, inorganic substance that is naturally occuring
What minerals characterize mafic rocks?
dark minerals- pyroxene, amphibole, olivine and mica In- gabbro Ex- basalt
What are the three types of plate boundaries?
divergent, convergent, transform
How do covalent bonds work?
elements share electrons
Stratovolcanoes (composite volcanoes)
form at subduction zones- Ring of Fire, large, symmetrical, steep summit, sloping flanks, layers of compositions of lavas and pyroclastic material
What physical properties are used to identify minerals?
hardness, specific gravity, color, luster, streak, cleavage, crystal form
What history does a course-grained phaneritic rock indicate?
indicate that magmas slowly cooled deep underground
What history does a porphyritic rock indicate?
indicates that a rock had time to cool before being extruded onto the surface of the earth
How do minerals form?
intense heat and pressure. Silicates in the magma form crystals with the magma cools
What are the three types of chemical bonds?
ionic, covalent, metallic
How do metallic bonds work?
ions are held together by their attraction to the electrons between them.
Shield Volcanoes
low viscosity, basalt, very large, broad, low sloped, no significant pyroclastic, form on ocean floors, Hawaii
Why did the earth differentiate into different layers?
minerals accumulated to form Earth, the high velocity impact of nebular debris and the decay of radioactive elements caused the temperate of our planet to increase steadily. During the time of intense heating, Earth became hot enough that iron and nickel began to melt. This melting produced liquid blobs of dense metal that sank toward the center of the planet. This process occurred rapidly and produced Earth's dense iron-rich core. This melting formed buoyant masses of molten rock that rose toward the surface, where they solidified to form the primitive crust.
Major features of ocean basins
ocean ridges, deep-sea trenches, fracture zones
How do different compositions of magmas form?
partial melting: some minerals in a rock melt while others don't magma differentiation: physical separation of minerals can change magma Magma mixing
Major features of continents
plains, plateaus, mountain ranges
How do rocks melt to form magma?
rocks in the mantle melt due to changes in pressure or the addition of water
What is the most common mineral class in the earth?
silicate class
What are the important mineral classes?
silicates, oxides, sulfides, sulfates, halides, carbonates, phosphates, mineraloid
Why are some magmas felsic and some mafic?
some magmas are richer in silica content (Felsic) while some are richer in basalt (mafic)
What is the pattern of magnetic anomalies in the sea floor?
stripes parallel to the mid-ocean ridges
How are igneous rocks classified?
texture and composition
What is continental drift?
the gradual movement of the continents across the earth's surface through geological time.
What is geology?
the science that deals with the earth's physical structure and substance, its history, and the processes that act on it.
What is the asthenosphere?
warm, ductile, small amount of melt and is contained entirely within the mantle.