EARTH 119 EXAM 1

What are the 8 most abundant elements in the Earth's crust?

(Oxygen (O), Silicon (Si), Aluminum (Al), Iron (Fe), Calcium (Ca), , Magnesium (Mg), Sodium (Na), and Potassium (K)

Magmas can change (evolve ) in their composition as they ascend through the lithosphere. What are the mechanisms that can lead to this change in composition?

- Partial Melting - Fractional Crystallization / Differentiation - Assimilation of Country Rock

Age of the Universe

13.7 billion years

What is the accepted age of our Universe (not the biblical age).

13.7 billion yrs

Age of oldest ocean floor

180 million years

age of solar system

4.6 billion years

The crystallization of mafic igneous rock begins at much higher temperatures than for felsic minerals. What are the respective temperatures for these?

600C Felsic 1200C Mafic

What is the radius of the Earth? The distance from its surface to the center of the core?

6378.1 km (3963.2 mi), 6371 km.

Who first proposed the concept of continental drift?

Alfred Wagner

Solids that do not possess an orderly arrangement of atoms (frequently cause by very rapid cooling) are called

Amorphous solid (glass)

What is the "asthenosphere" and why is it important when considering plate tectonics and seafloor spreading?

Asthenosphere - gooey, assists in the movement of the lithosphere. Non-newtonian layer below lithosphere

What physical conditions transform other rocks into "metamorphic rocks"?

Burial and heating

When minerals are broken, this breakage can occur along planes of weakness within the crystal. What do we call this property?

Cleavage

We are some measurable and observable properties of minerals that help us distinguish among them?

Cleavage, Crystal Habit, Density, Luster, Hardness

What are some observations that support the theory of tectonic plates on Earth?

Continental shape, ocean floor magnets, fossils, earths interior imaging, mountain ranges, climate

What is "isostacy"?

Continents (made of Felsic Rocks) "Float" Higher than Ocean Basins (made of Mafic Rocks) which "Sink" Lower into the Underlying Asthenosphere

Why does plate tectonics and seafloor spreading occur? Think in terms of what it does to the heat budget of the Earth

Convection

Based on fundamental principles of physics F=ma, and F=GmM/r2 ( you don't need these to calculate this!), it was determined that the Earth has an average density of 5.5 grams/cc. However, the rocks that we observe from the mantel and the crust have a density of only 3.5 and 2.7 g/cc, respectively. Where is the extra mass (weight) and what is its compostion?

Core, Iron

Chemical Bonds are primarily controlled by interactions among electrons. What are the two types of bonds, what characterizes each and which is forms the strongest bonds?

Covalent (strongest) and ionic

The Earth is constructed with 4 major realms reflecting different compositional and physical characteristics. What are the approximate depths to the boundaries between each of these?

Crust 10-70km U. Mantle ~700 km L. Mantle ~3000km Outer Core ~5000km Inner Core 6371km

What are some mechanisms or factors which lead to the minerals crystallizing from a magma (or water). For example what has to happen for a magma to begin forming solid minerals, or water to begin precipitating mineral?

Crystallization, bonding of minerals

How does the presence of water impact the melting point of minerals? Think about how we form magmas?

Decrease melt temperature

What is an igneous dike and how does it differ from and igneous sill?

Dike - intrusion formed when magma (molten rock) fills a fracture in older rocks. Sill - tabular sheet intrusion that has intruded between older layers of sedimentary rock

What is the intrusive rock name equivalent to an "andesite" extrusive rock?

Diorite

Red shifts noted in the radiation spectra of celestial objects show an expanding universe are analogous to the _____ effect observed as train passes an observer.

Doppler effect

What is the extrusive rock name equivalent to an intrusive "granite".

Feldspar

What is the most abundant mineral group present in the Earth's crust and mantle?

Feldspar

When the Universe formed after the Big Bang, what elements were most abundant directly after its formation?

Hydrogen and helium

In silicates, the building blocks or silicon and oxygen can be arranged in a crystal in many ways. What are the five different arranges of these building blocks?

Isolated tetrahedra, single chains, double chains, sheet, framework

Volcanic rocks (extrusive) have much small crystal sizes than intrusive rocks. Why?

It cools down quickly and doesn't have time to grow larger crystals

How do we know that the Earth is a sphere and not flat?\

It curves

Which characteristics of Earth's magnetic field played a major role in establishing the theory of plate tectonics?

Magnetism on the ocean floor caused convection of the iron core

At seafloor spreading centers, what kind of igneous rock is erupted and what distinctive structure does it form?

Mid-ocean ridges, basalt

What are the requirements for a solid to be classified as a "mineral"?

Naturally Occurring and Homogeneous Definable Chemical Composition Ordered Arrangement of Atoms to form a crystalline solid Possess distinct physical properties Inorganic

In nature we can have two different minerals even though the chemical composition is identical because they have a different crystal structure. What do we call these - for example aragonite and calcite (bot CaCO3)?

Polymorphs

Why is the Earth continuing to produce heat in the mantle? What kinds of reactions make this heat?

Pressure and temperature, radioactice decay

The atomic weight of an element is defined as the sum of what two subatomic particles?

Proton and neutron

How do we know the circumference of the Earth? (and even the Greeks were able to determine this)

Recognizing the curvature of the Earth and knowing the distance between the two cities enabled Eratosthenes to calculate the planet's circumference.

What geologic features or phenomena are present at divergent plate margins?

Ridges, earthquakes, volcanic activity

What is the rock cycle, and how does one type of rock (i.e., Igneous) become another type (i.e., sedimentary or metamorphic)?

Sediment - burial and compaction metamorphic - deformation and metamorphism igneous - crystallization of magma

What is the chemical formula for the mineral Quartz?

SiO2

What is decompressional melting and under what geologic setting is it responsible for the formation of magmas?

Temperature versus Pressure

What is accretionary heating, and how did it lead to the density stratification of the Earth (Formation of the Core, Mantle and Crust)?

The energy accumulated through the burial of heat by impacts as the planet grows by the accretion of planetesimals

How do we know the distance from the moon to the Earth?

We know, as did the Ancient Greeks, that the Moon travels around the Earth at a constant speed - about 29 days per revolution. The diameter of the Earth is also known to be about 12,875 km or 8,000 miles.By tracking the movement of the Earth's shadow across the Moon, Greek astronomers found that the Earth's shadow was roughly 2.5 times the apparent size of the Moon and lasted roughly three hours from the first to last signs of the shadow.

Columnar jointing, such as that phenomenon that created the structures in "Devils Tower" or "Devils Causeway" forms by what process?

When thick basalt lava flows cool, they tend to form hexagonal cracks, called columnar joints.

I have shown pictures of a "Porphyritic Andesite". What is a porphyry and how does it form?

a hard igneous rock containing crystals, usually of feldspar, in a fine-grained, typically reddish groundmass.

What are the three kinds of boundaries between tectonic plates

convergent, divergent, transform

Fine grained means

extrusive

You should have "Bowen's Reaction Series" imprinted in your memory. What minerals would you expect to find in an ultramafic rock versus a felsic rock?

felisc - quartz, feldspar, mica intermediate - amphibole Mafic - pyroxene ultraMafic - olivine

What is a pyroclast?

fragmented pieces of volcanic rock ejected upward

coarse grained (intrusive)

granite

Coarse grained means

intrusive

Mafic igneous rocks occur at which kinds of lithospheric plate interactions?

island arc and continental subduction

What is a pillow basalt? Where does it form?

lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or subaqueous extrusion.

Continents can grow in size through time. Beginning as small continents that merge together into larger plates. What are three ways continents "accrete"?

material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses.

Felsic and intermediate igneous rocks occur at which kinds of plate interactions?

ocean-continent, ocean-ocean convergent boundaries

We now know that rigid lithospheric plates move (or drift) relative to one another, floating on a asthenosphere that is plastic rather than rigid. How fast do plates move

rates of up to four inches (10 centimeters) per year

The Wilson cycle basically says the the World alternates between forming super continents which are then broken up, only to reform new super continents in the future. The last super continent was called Pangea (about 250 Ma --million years ago). What was the name of the supercontinent that existed about 1 billion years ago?

rodinea

We classify Igneous rocks based on their composition (which minerals are present) and based upon the texture. What is the rock name of a coarsely crystalline igneous rock composed of abundant quartz, K-Feldspar (Orthoclase), Muscovite?

ryolite

What do we call the building block for most silicate minerals and what is its chemical formula?

silica tetrahedron, (SiO4)4-

What two mechanisms are responsible for the formation of magmas?

temperature and pressure

Other elements formed by a process called nucleosynthesis. What is this and where does this occur?

the process that creates new atomic nuclei from pre-existing nucleons and nuclei