Fire and Ice
Fire formed Rocks
(Credit: Erin Todd, USGS. Public domain.)
Igneous rock (from the Greek word for fire) are rocks that were formed from magma deep inside the core of the Earth. There are two types of igneous rock: intrusive and extrusive. The intrusive rock occurs when magma is released and cools slowly over thousands or millions of years below the Earth's surface. This slow cooling process allows the crystals to grow and to form a coarse texture. The extrusive rock occurs when magma is released above the surface from a volcanic eruption or oozing fissure and cools quickly, shortening the time crystals can grow; therefore, a fine textured, volcanic rock is formed.
Ice, glacial retreat, and soil formation
Glacial till is the process of erosion and movement of materials through the expansion and contraction of glaciers. During glacial till, rocks are moved and broken apart. The outwashed sediments leave behind rocks, new soil, and piles of glacial debris at the leading edge of the glacier, called terminal moraines. With the work of soil scientists, there is evidence that ancient glaciers once covered what it now Canada and the northern portions of the United States.
Shown in cross section, this illustration depicts the various types of sediments associated with glaciation. [http://water.usgs.gov/edu/gallery/glacier-satellite.html]
Plant and landscape adaptations to fire
Paul S. Bieler, hosted by the USDA-NRCS PLANTS Database
The lodgepole pine (Pinus contorta), pictured above, has adapted to fire conditions by produces two types of closed cones. One is serotinous and the other is non-serotinous. The serotinous cones are closed tightly with resin, which melts in fire conditions, allowing the cone to open and release the seeds for a new generation of trees (NPS, 2019).
The ASU Library acknowledges the twenty-three Native Nations that have inhabited this land for centuries. Arizona State University's four campuses are located in the Salt River Valley on ancestral territories of Indigenous peoples, including the Akimel O’odham (Pima) and Pee Posh (Maricopa) Indian Communities, whose care and keeping of these lands allows us to be here today. ASU Library acknowledges the sovereignty of these nations and seeks to foster an environment of success and possibility for Native American students and patrons. We are advocates for the incorporation of Indigenous knowledge systems and research methodologies within contemporary library practice. ASU Library welcomes members of the Akimel O’odham and Pee Posh, and all Native nations to the Library.
