Below are examples of the symbols used in geologic diagrams and maps to represent specific kinds of rocks. If bedding, cross-bedding, ripples, fossils, distortion, or certain materials are present in the rock, the symbols are altered. To download the complete list of standard symbols, click here. Read more
Geologic Map Symbols
Volcano news: how slopes affect lava flows, challenge to traditional volcano model, Mauna Loa waking up
The summer of 2014 has been an exciting one for volcano science!
Easy Science: The Great Oxygenation Event
The Earth wasn't always a friendly place to live. Not only was it covered in lava and constantly eruption, its atmosphere was chocked with volcanic gases like carbon dioxide and sulfur dioxide. How and when did the atmosphere reach its current oxygen-rich state? This post will walk through the processes as well as some of the evidence that allows us to understand what happened. While I describe as a series of apparently discrete steps, it's important to remember that these processes sometimes overlapped and that they occurred over a span of time, often millions or billions of years.
How zircons help us date and understand the ancient earth
Small and unimposing at just fractions of a millimeter across, the igneous silicate mineral zircon (ZrSiO4) lays its claim to fame as the oldest earth material at 4.4 billion years old. The secret to zircon's success is its durability and tenacity. When other minerals break apart or turn into other minerals, zircon bravely trudges on. My former professor, Dr. Alex Glass of Duke University, described zircon as "the thing that never leaves," comparing zircon to a person who awkwardly remains at a house party long after all the other guests have left. He suggested that rather than diamonds, zircons should be the ultimate symbol of everlasting love. Read more →
Hawaiian volcano rift zones
In Hawaii, volcanoes form over a hot spot, an area where magma rises from the mantle and breaks through the crust. The Pacific plate moves northwest over the hot spot—which remains stationary—eventually carrying the old volcano away from the hotspot. A new volcano then begins to form, with repeated basaltic eruptions building a broad shield volcano. Read more →
Mafic & ultramafic rocks
Most geology students know what a basalt or gabbro is, but occasionally even introductory texts will refer to different mafic rocks and ultramafic rocks. This list very briefly describes a few of these, just enough to differentiate between them based on composition and formation.
Types of volcanic eruptions and their dynamics
This post will focus on the processes driving volcanic eruptions (for more details on all things volcano, visit this awesome site by SDSU). The most important factor controlling eruption type is the composition of the lava, which controls how much gas the lava contains. The more viscous the lava, the more gas it traps—and the more gas, the more explosive the eruption.
Types of volcanic rocks, lava, and deposits
Volcanic rocks are extrusive igneous rocks. There are two main groups: rocks that form from the solidification of lava flows (extrusive), and rocks that form from the compaction of solid volcanic fragments (pyroclastic). This post will cover the basics in easy-to-grasp bullet-point style that facilitates comparison between volcanic rocks. For information on eruption types, click here.
Types of meteorites
A meteorite is a rock (usually small but sometimes very large) that breaks off of an asteroid, planet, or comet, and falls from space to earth. Due to their immense age and the fact that many of them haven't changed since they formed, meteorites were essential in dating our solar system and continue to provide clues on what the early universe looked like. By recording traces of cosmic rays and solar wind and flares, meteorites allow us to reconstruct the space environment and behavior of our sun.
Meteoroid (in space) → Meteor (in atmosphere) → Meteorite (on earth)
Easy Science: how oil forms
In the late 1800s, the main use for petroleum was to produce kerosene for heating lamps. Gasoline, a byproduct of this process, was considered a waste; in Pennsylvania, this "waste product" was dumped into the river, where it sometimes caught fire! At the turn of the century, the appearance of the gasoline-powered engine would usher in the "Oil Age", forever changing the world's relationship with "black gold". Modern societies have grown to depend on this millions-years-old substance to function, guzzling over 30 billion barrels a year. Based on estimations of remaining reservoirs, we can keep this rate up through 2050-2150. Walking through the process of how oil forms underscores just how amazing the substance--a fossil from millions of years prior, surviving only be coincidence--really is.