Just like other science passages, the ACT Science Test wants to know what you can do rather than what you already know, so you won’t be required to have a vast knowledge of physical sciences. You already know all the Science knowledge you’ll need on Test Day from your high school Biology and Chemistry classes, and you’ll more than likely already be familiar with most of the scientific vocabulary the ACT Science Test uses. Focus on breaking down the passages analytically first. Let’s work on an short example of a Physical Science passage just like you might see on the real ACT! Keep in mind that the actual ACT Science passages will be a bit longer than this!

## Passage I

Geologists describe the orientation of sedimentary rock layers using two angles, “dip” and “strike.”  The dip indicates how far from horizontal the rock layer is tilted, and the strike indicates the compass direction along which the rock layer has been tilted.  For example, a dip of 1 degree indicates that a rock layer is nearly horizontal – it slopes downward at an angle of only 1 degree.  A strike of 1 degree indicates that the rock layer is tilted along a line running 1 degree east of north (i.e. almost due north), a strike of 90 degrees indicates that the rock layer is tilted along a line running 90 degrees east of north (i.e. due east), and so forth.

Which of the following describes a rock layer that is tilted vertically along a line running northeast?

(A) dip = 45 degrees, strike = 90 degrees

(B) dip = 90 degrees, strike = 45 degrees

(C) dip = 90 degrees, strike = 90 degrees

(D) dip = 180 degrees, strike = 90 degrees

According to the passage, a dip of 1 degree indicates that the rock layer is tipped 1 degree from the horizontal. We need to know the dip that corresponds to tilting the rock layer until it is vertical. The vertical line and the horizontal line make an angle of 90 degrees, so the dip is 90 degrees when the bed is tilted vertically. The passage also states that a strike of 1 degree indicates that the rock layer is tilted along a line running 1 degree east of due north, so a strike of 45 degrees indicates that the rock layer is tilted along a line 45 degrees east of due north, or northeast. The correct answer is (B).