Earth Explorations

Data rotations are done to put structural features back to original positions. In this episode we cover rotating data around vertical or horizontal axes, either parallel with or not parallel with strike, and rotating around an axis off horizontal or vertical.

Plotting a linear trend (1:10-2:50), plotting a line on a plane (3:15-4:30), Rake of lineation (4:30-6:25), apparent vs true dip problems (6:25-8:45), intersection line of two planes (8:45-9:20), angle between two planes (9:25-9:55), angle between a plane and a lineation (9:55-11:00), bisecting plane (11:00-12:00)

The first section is an overview of drone apps, and you can skip this if not interested to the other more directly appropriate geology apps.

There are many planar and linear measurements, sometimes hundreds, and you need a way to organize all this 3D data. Stereonets are here to the rescue.

Using all the concepts we have been covering, we put it all together and use a site in Morrison, CO. to do a complete basic geologic investigation and mapping project. We also cover the use of Adobe Illustrator to create geologic maps.

The procedures for construction, and the items to watch out for when constructing a geologic cross section of the geology below your feet.

Knowing the original sequence of rocks is essential for unravelling complicated structure. Having a stratigraphic column of the rocks in your area is a handy reference for the original sequence. And a Jacob's staff is used to construct such stratigraphic columns.

Once you've planned for your trip, and hit the ground of your field area, how will you conduct yourself to get the most data out of the time you have.

Before heading out to a field site with limited precious time, you should have a bulk of the work done to get the most out of your field experience.

This video covers basic clothing, basic gear (hammer, lens, compass) and more specific gear, and the general importance of maintaining safety in the field.

Besides measuring the attitude of rock layers, strike and dip can be used to measure any other planar feature like faults, joints, and foliation. We here introduce another measurement: dip and dip direction a.k.a. plunge and trend.

Strike and dip measurements are bread and butter for the field geologist, and learning how to take them accurately, consistently, and quickly are essential for the practicing geology fan. You must have the skills discussed in this episode down before you head out in the field.

Various ways are used to predict a volcanic eruption that can help move people out of harms way in time: gas and heat output, earthquakes, ground deformation, electrical resistivity, VLF emission, and historical analysis, and even strange animal behavior, all come in to play.

The ductile strain structural forms and low stress brittle strains are seen here with folding, boudinage, and jointing.

Geologic structures are formed as a result of rocks being strained by various stresses. Here we explore the stress and strain types, and then look at what brittle strain does in making faults, and how to distinguish them.

Avalanches, rock fall, landslides, debris flows, mudflows, and creeping soil are all met in this episode on mass movement.

Lava flows, blast impacts, suffocating gasses, climate change, release of latent toxics, direct release of toxics, ejecta of ash, lapilli, cinders, and bombs, pyroclastic flows, landslides, mudflows, lahars, and volcanic tsunamis.

When prediction is uncertain and potentially socially disruptive, it may be best to locate areas at risk, and zone for building codes that can reduce damage by not having weak levels, damping the building's response, or reducing the amount of energy entering the buildings.

We look at the various methods used to predict earthquakes, mention the few successes, and the many failures that make short term earthquake prediction difficult. But certain patterns can help us predict on longer time scales.

We cover all major quake dangers: shaking and the failure of buildings and slopes, influence of underlying substrate and bedrock in energy transmission and local shaking, wave interference and resonance, ground rupture, FIRE, sinkholes, liquefaction, gas emissions, sand boils, tsunamis, foreshocks and aftershocks.

We look at the history of detecting and measuring earthquakes and take a deeper dive into the modern methods of determining the size of earthquakes, their time of occurrence, their distance from the observer, the energy released by the event, and the resulting ground acceleration and damage that takes place.

We go through the six modes of earthquake generation: tectonics and isostasy, volcanoes, landslides, explosions and impacts, hydraulic pressure, and tidal forcing.

A look into use of S and P body wave reflection, refraction, and velocity changes to get a better picture of Earth's interior structure. We also examine Moonquakes with the same goal, and cover the sparse data from Mars.

Seismic waves can be broken into body waves within the Earth and surface waves trapped at the surface. Body waves can be further broken into P waves and S waves, and the surface waves are further divided into Love and Rayleigh waves. A full description of each is given here.

Corinth, Shesi, Lisbon, St. Lawrence River, New Madrid, San Francisco, Chile, Indonesian tsunami, Japan, Tibet, all shook up.

Stresses, and landforms seen at each of the three major plate boundaries: divergent, convergent, and conservative.

The deep time history of supercontinents on Earth, the structure of continents, and the prevalence of plate tectonics on other planetary bodies.

Sea floor spreading drives plate tectonics, but what drives sea floor spreading: conveyor belt motion of the asthenosphere, gravity sliding of the ridges, and slab pull at the trenches.

Going beyond the evidence given by Harry Hess, we explore the cumulative evidence that allowed geologists to accept plate tectonics before the end of the 1960's.

Harry Hess and Marie Tharp are the main heroes elucidating the mechanism for continental drift, and thus laying the groundwork for plate tectonics, in this week's episode.

An overview of the theory of Continental Drift with a focus on its promoter Alfred Wegener and his conception of the supercontinent of Pangaea.

Beyond radiometric dating, this episodes investigates some of the more common dating techniques. Also know there are other cosmogenic isotopes that can be used for dating in some ways, and a technique called optically stimulated luminescence.

We see why we can't date any rock as they must satisfy the requirements of absolute radiometric dating. Before ending with which types of rocks best suit the requirements, we also explore isochron dating; a method to probe the requirements and find age.

Here we investigate radiometric decay used as a clock for geologic time. Alpha and Beta decays are discussed along with the concept of a parent elements half life as it turns to daughter element.

An overview of the major Supereons, Eons, Eras, Periods, and more recent Epochs of geologic time. Some mnemonic devices are suggested as well.

This is the heartbreaking tale of a geologic hero, who mapped the whole of his country from concepts involving the law of fossil succession, which he showed to be so powerful in organizing rocks in sequence.

We examine the thermodynamic reasons why a mineral reaction may take place, why overstepping may occur, and how various crystal textures can form.

A look at the foliated rocks using parental materials of shale and basalt as principal markers for metamorphic grades and zones. We look into index minerals and general chemistry.

Starting with parent rocks of limestone, dolomite, and sandstone, we see how these mono-mineralic sedimentary rocks can become monomineralic non-foliated metamorphic rocks. But we will also see that with a bit more chemistry in the minerals and fluids, we can get more varieties of mineral forms. Marble and quartzite our our star players today.

This episode definitely requires mastery of episode 40, Metamorphic Chemistry 1, to fully appreciate. Get these two episodes under your belt, and you have a good start on metamorphic petrology.

A look at the phase rule and it's implications for determining the temperature and pressure levels in a metamorphic rock. These concepts can be applied to chemical systems beyond metamorphic processes.

A look at pressure and temperature in the Earth: lithostatic pressure and deviatoric pressure followed by variations in the geothermal gradient.

Our first metamorphic episode covers the definition of metamorphic rocks, the processes that make them, and the resulting textures which is the first go at classifying these rocks. We end with the various environments metamorphism takes place on Earth.

This episode explores as many depositional environments and the general characteristics of the sedimentary rocks that form in them as can be covered in under 15 minutes. This is also the last episode of sedimentary rocks before we move on to Metamorphic.

This episode covers the features seen in sedimentary rock that form after the sediment is initially deposited, but before it reaches metamorphism.

Scrape, scour, flute marks along with ripples, cross bedding, and rhythmic layers round off our list of primary sedimentary features this week.

Here we gain more information from sedimentary rocks by looking at their clast size, sorting, rounding, and the phenomenon of graded bedding.

When non-dissolved clasts are deposited and lithify, they form the clastic sedimentary rocks. Here we explore their naming and their common environments of deposition.

Here we look at the rocks which precipitate from evaporating water, accumulate from organic skeletons, and form from hot fluids both on the surface and underground.

Here we look into the processes of weathering, erosion, deposition, and lithification. We examine the agents of erosion, and how this in turn leads to the two types of deposition, which lithify into the two types of sedimentary rocks: chemical and clastic.

The major intrusive bodies of plutons: dikes, sills, batholiths, stocks, laccoliths, and lopoliths. We then cover the major extrusive features: lava flows of pahoehoe and aa, and pyroclastic materials.