In geology and engineering geology, rocks formed by cooling and solidification of magma at relatively shallow depth (subvolcanic level) are called what? Choose the most accurate term.

Introduction / Context:
Igneous rocks are classified by their depth of emplacement: deep-seated, shallow intrusive, or surface extrusive. The question checks your knowledge of the specific term for shallow intrusive bodies.

Given Data / Assumptions:

• Cooling occurs below the surface but not at great depth.
• Textures are typically medium to fine due to faster cooling than plutonic bodies.

Concept / Approach:

Shallow intrusive rocks formed at subvolcanic levels are termed hypabyssal. Plutonic refers to very deep and slow cooling (coarse texture), whereas volcanic refers to surface lava flows and pyroclastics (very rapid cooling, fine to glassy). “Igneous rocks” is a broad category, not a specific depth term.

Step-by-Step Solution:

Verification / Alternative check:

Examples include dykes and sills showing porphyritic to fine crystalline textures consistent with intermediate cooling rates.

Why Other Options Are Wrong:

Plutonic: too deep. Volcanic: extrusive at surface. Igneous (generic): not a depth-based subclass.

Common Pitfalls:

Confusing hypabyssal with volcanic due to fine grains; overlooking intrusive vs extrusive context.

Final Answer:

Hypabyssal rocks