DSST® practice test

Free DSST Introduction to Geology Practice Test (2026)

This is a set of 25 original practice questions that follow the official DSST Introduction to Geology content outline and its topic weights, each with a short explanation. Answer all 25, then read the explanations to see which topics need more study.

  • 25 questions
  • 4 topics from the official outline
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The practice test

25 questions

Question 1 of 25A radioactive isotope has a half-life of 700 million years. A mineral that started with only the parent isotope now holds 25% of its original parent atoms. How old is the mineral?
Question 2 of 25Which arrangement of rocks forms a common trap for oil and natural gas?
Question 3 of 25Shale is subjected to steadily increasing temperature and pressure. In what order does it change?
Question 4 of 25On the Mohs hardness scale, quartz has a hardness of 7. Which mineral can scratch quartz?
Question 5 of 25After a thick ice sheet melts, the land that was under it slowly rises over thousands of years. What explains this uplift?
Question 6 of 25An anticline has been eroded flat, exposing its layers at the surface. Where are the oldest rocks found?
Question 7 of 25Why do sinkholes and caves form most often in regions underlain by limestone?
Question 8 of 25Along a fault, the hanging wall has moved down relative to the footwall. What kind of stress mainly produces this fault?
Question 9 of 25Seismographs on the far side of Earth from a large earthquake record no direct S waves. What does this S-wave shadow zone reveal?
Question 10 of 25In several farming valleys, heavy pumping of groundwater has made the land surface sink by several meters. What is the main cause?
Question 11 of 25Composite volcanoes (stratovolcanoes) erupt far more explosively than shield volcanoes. Which property of their magma best explains this?
Question 12 of 25A basalt dike cuts across three layers of sandstone and shale. Which principle shows that the dike is younger than all three layers?
Question 13 of 25Where does a meandering stream mainly deposit sediment?
Question 14 of 25Longshore drift carries sand past a headland and builds a narrow ridge of sand that extends into the open water of a bay. What is this feature?
Question 15 of 25A light-colored, coarse-grained igneous rock is rich in quartz and potassium feldspar. What rock is it?
Question 16 of 25A sand dune forms where a steady wind blows in one direction. Where is the dune's steep slip face?
Question 17 of 25A sandstone is made of well-sorted, well-rounded quartz grains. What does this most likely indicate about its sediment?
Question 18 of 25Which reservoir holds the largest share of Earth's fresh water?
Question 19 of 25On a grassy hillside, fence posts and old trees lean downhill, but there has been no sudden slide. Which type of mass wasting is most likely occurring?
Question 20 of 25The Andes Mountains run parallel to a deep ocean trench and contain a chain of andesitic volcanoes. At what type of plate boundary did they form?
Question 21 of 25Which chemical weathering process turns feldspar into clay minerals?
Question 22 of 25Rocks of matching age and magnetic polarity are found in parallel stripes at equal distances on both sides of a mid-ocean ridge. What does this pattern best support?
Question 23 of 25Several cirques erode a mountain from different sides, leaving a sharp, pyramid-shaped peak. What is this peak called?
Question 24 of 25Which sequence of processes in the rock cycle turns an exposed granite into sandstone?
Question 25 of 25An igneous rock has large, well-formed crystals set in a fine-grained groundmass. What does this porphyritic texture indicate?

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