In a previous post, we discussed the spectacular columnar basalt formed under a very slow (over centuries!) cooling rate. The cooling rate controls the texture of basaltic lavas. Now, let's talk pillows. Pillow basalts are formed on the opposite end of the cooling rate spectrum.
Pillow basalt is a volcanic igneous rock that forms when lava of basaltic compositions erupts underwater. But, unlike columnar basalt, pillow basalt is formed in the fastest cooling environment possible on Earth. Underwater, where the water steals the lava's heat so rapidly (instantly) that it forms a unique texture, pillows. It's also an impressive example of exothermic and endothermic reactions! The liquid lava is going through an exothermic process as it turns to basaltic rock because its losing heat to the ocean and therefore cooling—contracting. The ocean water goes through an endothermic process because it absorbs the heat of the lava.
Our Ward's Science Geologist, Amelia, explains the what, why, and where of pillow basalts and the scientific facts behind their formation. Put pillow basalt concepts to bed by including this activity in your lesson plan!
Use our study guide and teacher's answer key to reinforce the concepts covered in this post.
Ward's® Introductory Mineral Collection
Beginning geology students will easily recognize each of the wide range of physical properties when they examine the basic minerals. High-quality specimens, cut by Ward's geologists.
Rock and Mineral Test Kit
A handy zippered pouch contains all the equipment you need to perform a variety of physical properties tests on rocks and minerals.
Ward's® Mohs' Hardness Scale Collection
Our most popular collection includes nine numbered samples, streak plate, nail, glass slide, and copper strip. All samples are pure crystalline forms to ensure accurate test results.
Ward's® Essentials Exothermic Reactions Lab Kit
Experience an exothermic reaction and create a heat pack.