Connection to the Earth Science Curriculum
Key Earth Science/Geological Vocabulary Words-
joint: a fracture in rock along which there has been no displacement.
rift: a fault.
flow: a stream of molten or solidified lava.
basalt: a dark-colored fine-grained extrusive igneous rock.
Houghton Lava Flow
This site which is behind a strip mall in the Keweenaw Peninsula provides a great opportunity to readily see volcanic flow from the Keweenaw Rift.
Coordinates- N47o06.686’ W088o35.084’
Michigan has ancient rock that dates over 3.5 billion years old that originated from tectonic plate collisions and eruptions from volcanoes. This site is a fresh outcropping that was exposed through the building of the strip mall. It is a great view of lava flow anatomy. You can see where one flow begins and another ends. Look for the bubbly top layer to connect with the dark bottom layer of the next flow. The image below will help you to recognize where one flow begins and another ends. Look for the contact points.
Figure 1.Lava flow. Anatomy of a lava flow.
The Hawaiian Island lava flows are smooth at the surface and are called “pahoehoe”. The lava flows in the Keweenaw also have a smooth surface. These smooth surfaces of basalt contained bubbly (vesicles) areas that then filled up with minerals of various colors.
Logging Q1: What different colors do you see in this lava flows surface?
At this site, you also note there is more than one lava flow. You notice that the flows are not laying horizontal, but are on an angle. The top of the flow is a bilious green that is bubbly with the different mineral colors in the bubbles. The bottom portion of the flow is a black color. Find the top of a lava flow.
Figure 2. Houghton Lava Flow. MiTEP participants viewing the Houghton Lava Flows.
Logging Q2: How do you know where one flow begins and one ends?
Logging Q3: How many lava flows are there?