Science Earth and Space Science Flashcards

During a lunar eclipse, the Moon passes through Earth's umbra and takes on a reddish hue. Which phenomenon is primarily responsible for this 'blood moon' appearance?

Answer: Rayleigh scattering of sunlight through Earth's atmosphere bending red wavelengths onto the Moon

During a total lunar eclipse, Earth's atmosphere refracts sunlight around the planet. Shorter blue wavelengths are scattered away (Rayleigh scattering), while longer red wavelengths bend through the atmosphere and illuminate the Moon, giving it a reddish color — the same physics that makes sunrises and sunsets appear red.

A geologist studying a rock sequence notices that a layer of marine limestone containing trilobite fossils sits directly beneath a layer of volcanic ash, which is directly beneath a layer containing dinosaur fossils. If no major unconformities exist, what conclusion is best supported?

Answer: The volcanic event occurred after trilobites but before dinosaurs existed in this region

The principle of superposition states that in undisturbed rock sequences, older layers lie below younger ones. Since the trilobite-bearing limestone is lowest, it is oldest. The ash layer is intermediate in age, and the dinosaur layer is youngest. This means the volcanic eruption occurred after the trilobites' time period but before dinosaurs existed in this location — a straightforward application of relative dating.

Venus and Earth are nearly identical in size and mass, yet Venus has a surface temperature of about 465°C while Earth's average surface temperature is about 15°C. The primary driver of this extreme difference is best explained by:

Answer: Venus has a dense CO₂ atmosphere that traps outgoing infrared radiation far more effectively than Earth's atmosphere

Venus receives about 1.9 times more solar energy than Earth (not 10 times), but its extreme temperature is overwhelmingly due to its thick CO₂ atmosphere (96.5% CO₂), which creates an intense runaway greenhouse effect. This atmosphere traps outgoing infrared radiation so efficiently that the surface temperature far exceeds what solar proximity alone would cause — Venus is actually hotter than Mercury despite being farther from the Sun.

Which type of seismic wave cannot travel through Earth's outer core, and what does this property reveal about the outer core's composition?

Answer: S-waves; the outer core must be liquid because S-waves (shear waves) cannot propagate through fluids

S-waves (secondary or shear waves) require a rigid medium to propagate because they move particles perpendicular to the direction of wave travel. Liquids cannot sustain shear stress, so S-waves cannot pass through them. The fact that S-waves disappear in a 'shadow zone' on the far side of Earth's outer core is key evidence that the outer core is in a liquid (molten iron-nickel) state, even though the inner core is solid.

A star with 8 times the mass of our Sun will most likely end its life cycle as which of the following, and why?

Answer: A neutron star or black hole, because its core mass after the supernova exceeds the Chandrasekhar limit for white dwarfs

Stars with more than approximately 8 solar masses end in a core-collapse supernova. If the remnant core exceeds about 1.4 solar masses (the Chandrasekhar limit), electron degeneracy pressure cannot halt collapse, and it becomes a neutron star. If the remnant exceeds roughly 2–3 solar masses (the Tolman-Oppenheimer-Volkoff limit), neutron degeneracy pressure also fails and a black hole forms. Lower-mass stars like our Sun end as planetary nebulae with white dwarf cores.

The Milankovitch cycles describe periodic variations in Earth's orbital parameters. Which combination of Milankovitch cycle effects would most strongly promote the onset of an ice age?

Answer: Minimum axial tilt combined with perihelion occurring during Northern Hemisphere winter

Ice ages are thought to begin when Northern Hemisphere summers are cool enough that winter snow persists year-round and ice sheets expand. Minimum axial tilt (approximately 22.1°) reduces seasonal contrast — summers are cooler and winters are milder. When perihelion (Earth closest to Sun) occurs during Northern Hemisphere winter, the hemisphere receives slightly more solar energy in winter but less in summer, further cooling summers. Together these factors allow ice to accumulate. Most land mass is in the Northern Hemisphere, making this hemisphere's summer temperatures the primary driver of glaciation.