Tectonic Processes (created using Knowt AI)

Flashcards generated from physical geography lecture notes covering plate tectonics, rock classification, earthquake mechanics, and volcanic structures.

What percentage of the asthenosphere is estimated to be partially molten?

Approximately $10\%$

According to Alfred Wegener, what are the six proofs for continental drift?

Coastline fit, geologic fit, paleoclimatology, paleoglaciation, fossil correlation, and paleomagnetism.

At what rate is the Pacific plate moving northward relative to the North American plate along the San Andreas fault?

At approximately $5\,cm/year$

What is the structural difference between intrusive and extrusive igneous rocks?

Intrusive igneous rocks form from magma that cooled at depth and are generally coarse-grained, whereas extrusive igneous rocks form from lava that cooled on the surface and are generally fine-grained.

How is the sedimentary rock Arkose specifically defined in terms of its composition?

Arkose is composed mainly of sand-sized particles of quartz and feldspar, with feldspar making up more than $25\%$ of the total.

Which parent sedimentary rocks undergo metamorphism to form slate, quartzite, and marble?

Shale metamorphoses into slate, sandstone metamorphoses into quartzite, and limestone metamorphoses into marble.

What is the distinction between an earthquake's focus and its epicentre?

The focus is the exact location within the earth where the earthquake occurs, while the epicentre is the spot on the earth's surface directly above the focus.

What are the depth classifications for shallow earthquakes and deep focus earthquakes?

Shallow earthquakes occur at depths between $1.6\,km$ and $96\,km$, while deep focus earthquakes occur at depths between $96\,km$ and $960\,km$.

How does the Theory of Isostasy explain equilibrium using the floating ice analogy?

It explains that continental blocks constantly seek equilibrium like a block of ice floating in water with $11\%$ above and $89\%$ below; if material is eroded, the crust readjusts upward to restore the ratio.

What were the magnitude, date, time, and epicentre location of the 1994 Los Angeles earthquake?

The earthquake occurred on January 17th, 1994 at 4:31 a.m., measured $6.6$ on the Richter scale, and had its epicentre $36\,km$ north of downtown Los Angeles in Northridge.

What is the difference between earthquake magnitude and earthquake intensity?

Magnitude measures the total energy released and ground motion (single value on the Richter scale), while intensity measures the localized effects produced at different places (variable values on the modified Mercalli scale).

What catastrophic event occurred at Pachena Bay on January 26, 1700?

An earthquake measuring $9\text{-plus}$ on the Richter scale struck the Cascadia Fault, causing the land to drop $1\,m$ and generating a $10$ to $15\,m$ high tsunami that destroyed the village of Loht'a.

At what speeds and directions are the North American plate and the Juan de Fuca plate moving relative to each other?

The North American plate moves west at $2\,cm/year$ and the Juan de Fuca plate moves east at $2.5\,cm/year$, producing a total convergence rate of $4.5\,cm/year$.

How does chemical composition affect the viscosity and flow of lava?

Silica-rich lavas (e.g., andesite) have high viscosity, making them thick and slow-moving, whereas iron- and magnesium-rich lavas (e.g., basalt) have low viscosity, making them fluid and fast-moving.

How do slope angles and eruption types differ between cinder cones and shield cones?

Cinder cones have steep slopes ($30^\circ - 40^\circ$) formed from violent ash/cinder eruptions, whereas shield cones have gentle slopes ($10^\circ - 20^\circ$) formed from quiet basalt lava flows.

What is a nuée ardente in the context of volcanic eruptions?

A nuée ardente is a rapidly moving, superheated cloud of gases (such as hydrogen, carbon monoxide, sulphur, and chlorine) released during a explosive volcanic eruption.

What are the structural definitions of a dike, a sill, a laccolith, and a batholith?

A dike is magma cooled in a vertical crack; a sill is magma flowing horizontally between sedimentary strata; a laccolith is a dome of igneous rock raising overlying strata; and a batholith is a large magma storage basin several kilometres thick.

What constant subsoil temperature is utilized by the geothermal heating system installed in Vancouver?

A constant subsoil temperature of $50^\circ F$