When volcanic lava solidifies, it becomes

Answer choices

1. A

   Unclear Impact9% picked this

   The changes in the direction of the Earth’s magnetic field are determined by the chaotic movement of iron-containing liquids

   Without knowing whether the chaotic movement of iron-containing liquids in the Earth's outer core is a sudden thing that changes or something that shifts gradually over time, it's hard to use this to say that the shifts in magnetic field are quick.

   9%
2. B

   No Impact7% picked this

   There has not been a change in the direction of the Earth’s magnetic field since scientists have begun measuring the direction

   The time scale of when scientists started measuring this is probably a couple hundred years, which is essentially an instant, on the timescales that we're talking about (hundreds of thousands of years). And if anything, the fact that the direction hasn't changed since we started measuring helps the author argue that it doesn't change quickly.

   7%
3. C

   No Impact10% picked this

   The direction of the Earth’s magnetic field has undergone a complete reversal several times over the

   If we were learning that the magnetic field has reversed several times within the last hundred thousand years, that would ruin the author's conclusion. But since the author thinks it changes every few hundred thousand years, she'd be expecting it to reverse several times (or more) over the past few million years.

   10%
4. D

   Correct69% picked this

   A lava flow has been found in which the direction of magnetization in the center of the flow differs significantly from that on the

   Why this is right

   This answer suggests that the magnetic field reversed over the course of two weeks. Lava that cooled at the start of that period is pointing in a different direction than lava that cooled a couple weeks earlier. And lava always matches the direction of the magnetic field, implying that the direction of the field shifted over the course of two weeks.

   Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

   69%
5. E

   No Impact5% picked this

   Since the rate at which molten lava solidifies depends on the temperature and altitude of the environment, some lava flows from volcanoes in certain

   The fact that it takes years to solidify doesn't really give us any way to say that the magnetic field changes direction quickly. We'd have to also know that over the course of these years of cooling, the direction that the cooled lava is pointing has shifted.

   5%