Interpreting the Earth

Practical and philosophical ways earth scientists interpret ancient environments, climates, oceans, volcanoes, fossils, earth events

 

How Geologists Interpret Ancient Environments #1. Getting started

How Geologists Interpret Ancient Environments #2. Ruffles and Desiccation

How Geologists Interpret Ancient Environments #3. A Philosophical Interlude

How Geologists Interpret Ancient Environments #4. Someone passed by this way – Tracks, trails, impressions and foot prints

How Geologists Interpret Ancient Environments #5. Sand to Stone = Sandstone; A remarkable Transformation

How Geologists Interpret Ancient Environments #6. When Time Goes Missing

How Geologists Interpret Ancient Environment. #7 Budget Surpluses and Budget Deficits

How Geologists Interpret Ancient Environments.  #8 A Forty Million Year Old Fossil Forest

How Geologists Interpret Ancient Environment, #9. The Oil Kitchen Rules

Marrying Fossils, Isotopes and Geological Time

Throwing the celestial dice

Submarine landslides; danger lurks in the ocean deep

When nature casually flicks a finger at us

Liquefaction; more than a sloppy puddle at the beach

A Gaggle of Goose Barnacles

Biomarkers; forensic tools for hydrocarbon fingerprinting

The (not so) Great Dying; Permian extinctions

Burnt soles: black sand beaches in New Zealand

Darwin Day, with apologies to Abraham Lincoln

Polar bears do not live in the Antarctic, there are no Penguins in the Arctic. The asymmetry of the poles

Ropes, pillows, and tubes; modern analogues for ancient volcanic structures

Rip currents – you have been warned

Crème brûlée, jelly sandwich, and banana split; the manger a trois of layered earth models

The Burrens of County Clare; An understated beauty

Tidal waves; prisoners of celestial forces

Bluebottle entanglements; or how to ruin your day at the beach

Crossing the harbour bar

Difficulty breathing: The Atacama salt lakes

Beach microcosms and river analogues

Beneath the ice; Greenland’s bedrock

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Conjugate fractures and en echelon tension gashes – indicators of brittle failure in Old Red Sandstone, Gougane Barra, County Cork, Ireland.
Mohr-Coulomb failure criteria
A montage of stress transformation paraphernalia and rock deformation
Mohr circles and stress transformation
The Marlborough strike-slip fault array extends north from the dextral Alpine Fault transform; faults continue across Cook Strait to join the North Island Dextral Fault Belt in the Wellington region (central Aotearoa New Zealand). In Marlborough and beneath Cook Strait there are several pull-apart basins formed at releasing bend stepovers. Sandbox analogue models can help us decipher the mechanical and kinematic processes that produce structures like these. Base image from NASA – International Space Station 2003.
Strike-slip analogue models
Scaled sand-box experiments are an ideal medium to observe rock deformation that, in this example, involves synkinematic deposition during rift-like crustal extension. The choice of model materials, in addition to imposed boundary conditions such as strain rates, will determine the outcome of the experiment. Dry sand was chosen for this model because its brittle behaviour under the model conditions is a good representation of natural rock failure. Diagram modified slightly from Eisenstadt and Sims, 2005, Figure 3a.
Analogue structure models: Scaling the materials
The relationship between inertial and gravitational forces expressed by the Froude number (Fr) is reflected by the changes in surface flows and the formation-decay of stationary (standing) waves. Fr < 1 reflects subcritical (tranquil) flow; Fr>1 supercritical flow. Although the Froude number can be determined experimentally, it can also be eased out of a dimensional analysis of the relevant hydrodynamic variables.
Model dimensions and dimensional analysis
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