Pillow basalts,shown below,attain their distinctive blob-like shapes because their parent lavas do not travel far prior to solidification.This is because the parent lavas ____________.
A) are completely devoid of volatiles and thus travel slowly
B) erupt underwater and thus cool very quickly
C) are highly felsic and thus travel slowly
D) are ultramafic and thus freeze at exceptionally high temperatures

Question

Pillow basalts,shown below,attain their distinctive blob-like shapes because their parent lavas do not travel far prior to solidification.This is because the parent lavas ____________. 
A) are completely devoid of volatiles and thus travel slowly 
B) erupt underwater and thus cool very quickly 
C) are highly felsic and thus travel slowly 
D) are ultramafic and thus freeze at exceptionally high temperatures

Quizplus · Accepted Answer

Pillow basalts are formed when basaltic lava erupts underwater, causing rapid cooling and solidification. This results in the distinctive blob-like or pillow shapes seen in these rocks. Therefore, option B - the parent lavas erupt underwater and thus cool very quickly - is the most appropriate choice. Option A is incorrect, as the presence or absence of volatiles does not necessarily determine the speed of lava flow. Option C is also incorrect, as felsic lavas are typically more viscous and prone to explosive eruptions, but this does not mean they cool more slowly. Option D is incorrect, as ultramafic lavas are usually hotter and less viscous, so they tend to flow more easily and cover greater distances before solidification.

Pillow Basalts,shown Below,attain Their Distinctive Blob-Like Shapes Because Their Parent