Nav: Home

Landscape evolution and hazards

March 31, 2016

Boulder, Colo., USA: Landscapes are formed by a combination of uplift and erosion. Uplift from plate tectonics raises the land surface; erosion by rivers and landslides wears the land surface back down. In this study, Georgina L. Bennett and colleagues examine the interplay of uplift and erosion along the coast range of Northern California to understand how the modern topography is built.

This region is unique in that a wave of uplift is sweeping north through the Coast Range, allowing geoscientists to document the erosional response and assess the timescale of the process. Bennett and colleagues find that rivers cut down through the uplifting land surface, steepening surrounding hillslopes and triggering landslides when hillslope angles reach a limit.

Landslides are the main erosional process balancing uplift in the region. However, intriguingly, they may also have a negative feedback to ongoing erosion, through the delivery of large resistant rocks to rivers that act to armor the riverbed from ongoing erosion. Thus the erosion of parts of the Coast Ranges in response to uplift may be delayed. These findings have implications for understanding landscape evolution, as well as hazards such as landslides.

FEATURED ARTICLE Landslides, threshold slopes, and the survival of relict terrain in the wake of the Mendocino Triple Junction
Georgina L. Bennett et al., Dept. of Geological Sciences, University of Oregon, 1275 E 13th Ave, Eugene, Oregon 97403-1272, USA. This article is online at

GEOLOGY articles are online Representatives of the media may obtain complimentary articles by contacting Kea Giles at the e-mail address above. Please discuss articles of interest with the authors before publishing stories on their work, and please make reference to GEOLOGY in articles published. Non-media requests for articles may be directed to GSA Sales and Service,

Other recently posted GEOLOGY articles highlighted below:

In-situ oxygen isotope records of crustal self-cannibalization selectively captured by zircon crystals from high-δ26Mg granitoids
Hui Je Jo et al., Dept. of Isotope Geochemistry, Korea University of Science and Technology, Daejeon 305-350, Republic of Korea. This paper is online at

Granitoids, the chemically evolved quartzofeldspathic plutonic rocks, are the most abundant rock types in Earth's continental crust. Although there is still no single universally accepted solution to the problem of granite petrogenesis, it becomes increasingly manifest that most granitoid rocks contain the recycled crustal component. The robust mineral zircon is an excellent recorder of the recycling process by virtue of its famous physicochemical durability. When combined with biotite magnesium isotopes, zircon oxygen isotopes of Mesozoic-Cenozoic granitoids in the southeastern margin of the Korean Peninsula provide compelling evidence for the involvement of surface rocks into the shallow magma system. Single magmatic zircon crystals became progressively enriched in the light oxygen isotope toward their rims, selectively in granitoid rocks containing biotite enriched in the heavy magnesium isotope. Such a concomitant isotopic variation is explained by the recycling of weathered surface rocks that experienced hydrothermal alteration after the crystallization of the zircon core. This situation would have been best achieved through assimilation of roof rocks around the volcanic center, which is conventionally referred to as "crustal cannibalization." This research shows that the combined stable isotope data from plutonic rocks sensitively detect the input of surface rocks that have now been eroded away.

Rapid ice sheet retreat triggered by ice stream debuttressing: Evidence from the North Sea
Hans Petter Sejrup et al., Dept. of Earth Science, University of Bergen, Allegaten 41, 5007 Bergen, Norway. This article is online at

Warming air and ocean temperatures are causing losses in the mass of existing ice sheets and it is thought that the long-foretold collapse of part of the Antarctic Ice Sheet has now been triggered and expected to be irreversible over the next hundreds of years. Such predictions, via numerical ice sheet modelling, are sensitive to the formulation of the mechanics of flow and the parametrisations chosen, and yet few opportunities exist for assessing model robustness at timescales beyond the observational record of tens of years. In this study, Hans Petter Sejrup and colleagues use fresh discoveries of glacial landforms in the North Sea to reconstruct the maximum extent of the ice sheet during the last glacial stage, finding that it underwent dramatic disintegration at around 18,500 years ago. They reconstruct collapse, triggered by grounding line retreat of its primary ice stream which de-buttressed adjacent British and Norwegian ice masses, and whose unzipping was accompanied by drainage of a large ice-dammed lake. The discovery of these major events provides an opportunity to improve understanding and modelling of the disintegration of marine-based ice sheets, and the complex interplay between ocean circulation and the cryosphere.

Solute sources and geochemical processes in Subglacial Lake Whillans, West Antarctica
Alexander B. Michaud et al., Dept. of Land Resources and Environmental Sciences, Montana State University, Bozeman, Montana 59717, USA. This paper is OPEN ACCESS online at

Subglacial Lake Whillans (SLW), West Antarctica, is an active component of the subglacial hydrological network located beneath 800 m of ice. The fill and drain behavior of SLW leads to long (years to decades) water residence times relative to those in mountain glacier systems. Here, Alexander Michaud and colleagues present the aqueous geochemistry of the SLW water column and pore waters from a 36-cm-long sediment core. Stable isotopes indicate that the water is primarily sourced from basal-ice melt with a minor contribution from seawater that reaches a maximum of ~6% in pore water at the bottom of the sediment core. Silicate weathering products dominate the crustal (non-seawater) component of lake- and pore-water solutes, and there is evidence for cation exchange processes within the clay-rich lake sediments. The combination of significant seawater and crustal components to SLW lake and sediment pore waters in concert with ion exchange processes result in a weathering regime that contrasts with other subglacial systems. The results also indicate cycling of marine water sourced from the sediments back to the ocean during lake drainage events.

Crustal accretion at a sedimented spreading center in the Andaman Sea
Aurélie Jourdain et al., Institut de Physique du Globe de Paris, Sorbonne Paris Cité, UMR7154-CNRS, 1 rue Jussieu, 78238 Paris Cedex 05, France. This article is online at

Through the interpretation of high resolution seismic profiles in the Andaman Sea, Jourdain and colleagues provide the first complete model of the magmatic and tectonic processes during oceanic crust emplacement below sedimented spreading centers. It is shown that the sediments are incorporated in crustal accretion process, where interaction with magma lenses creates a heterogeneous upper crust between the recent sediments and the lower igneous crust. For the first time on a slow-spreading center, the presence of multiple magma lenses on axis at different depth has been imaged. Also, within the axial valley, faults are steeply dipping (65-75 degrees) in a staircase pattern and their base coincides with shallow dipping (30 degrees) reflections. These low angle faults could define the zone of extension and magmatism. They evolve during accretion, back-tilting the upper crust. Thus, as the sediments mix with sill/dike intrusions, these sequences are rafted away from the axis, rotated and buried due to subsidence and faulting, forming the upper oceanic crust.

Identification of the short-lived Santa Rosa geomagnetic excursion in lavas on Floreana Island (Galapagos) by 40Ar/39Ar geochronology
Andrea Balbas et al., College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA. This article is online at

Convecting fluid in Earth's core that generates and controls Earth's magnetic field is known as the geodynamo. Mechanisms that control the goedynamo are not well defined, and Earth's magnetic field varies in strength and orientation through time. Changes in the field can be dramatic, resulting in large losses in field strength and full reversals of the field's orientation. It is well accepted that large changes in field orientation are also accompanied by large reductions in field strength. It is also well accepted that the orientation of the field can change dramatically and then return to its previous polarity state. These large changes in field orientation that do not result in a polarity reversal are known as geomagnetic excursions. In this study, Andrea Balbas and colleagues define that a geomagnetic excursion known as the Santa Rosa Excursion occurred ~926,000 years ago and was accompanied by an 86% reduction in field strength. Their data combined with other natural archives illustrate that this event had global significance. Balbas and colleagues suggest that the entirety of the excursion and recovery occurred in a time interval as short as 3,000 years. This work highlights similarities between the well-known Laschamp Excursion and the Santa Rosa Excursion indicating that dramatic short-lived excursions can occur during both polarity conditions (normal or reversed).

Geological Society of America

Related Magnetic Field Articles:

Understanding stars: How tornado-shaped flow in a dynamo strengthens the magnetic field
A new simulation based on the von-Kármán-Sodium (VKS) dynamo experiment takes a closer look at how the liquid vortex created by the device generates a magnetic field.
'Quartz' crystals at the Earth's core power its magnetic field
Scientists at the Earth-Life Science Institute at the Tokyo Institute of Technology report in Nature (Fen.
Brightest neutron star yet has a multipolar magnetic field
Scientists have identified a neutron star that is consuming material so fast it emits more x-rays than any other.
Confirmation of Wendelstein 7-X magnetic field
Physicist Sam Lazerson of the US Department of Energy's Princeton Plasma Physics Laboratory has teamed with German scientists to confirm that the Wendelstein 7-X fusion energy device called a stellarator in Greifswald, Germany, produces high-quality magnetic fields that are consistent with their complex design.
High-precision magnetic field sensing
Scientists have developed a highly sensitive sensor to detect tiny changes in strong magnetic fields.
Brilliant burst in space reveals universe's magnetic field
Scientists have detected the brightest fast burst of radio waves in space to date -- locating the source of the event with more precision than previous efforts.
Optical magnetic field sensor can detect signals from the nervous system
The human body is controlled by electrical impulses in the brain, the heart and nervous system.
What did Earth's ancient magnetic field look like?
New work from Carnegie's Peter Driscoll suggests Earth's ancient magnetic field was significantly different than the present day field, originating from several poles rather than the familiar two.
Just what sustains Earth's magnetic field anyway?
Earth's magnetic field shields us from deadly cosmic radiation, and without it, life as we know it could not exist here.
Ironing out the mystery of Earth's magnetic field
The Earth's magnetic field has been existing for at least 3.4 billion years thanks to the low heat conduction capability of iron in the planet's core.

Related Magnetic Field Reading:

Power Tools for Health: How Pulsed Magnetic Fields (Pemfs) Help You
by Msc William Pawluk MD (Author), Caitlin Layne (Author)

Power tools revolutionized the building of your family home.
Now they will revolutionize your health.

Power Tools for Health will teach you to how to:
- treat new or chronic health conditions like pain, anxiety, insomnia, diabetes and injuries
- avoid annoying or potentially harmful side effects from pharmaceuticals or other treatments
- enhance and accelerate recovery from surgery

Research shows PEMFs accelerate the healing of almost any cell, tissue, organ, or condition.
Unlike much of modern medicine, which mostly focuses on symptom... View Details

Know Your Magnetic Field: Change Your Thinking, Change Your Life.
by William E. Gray (Author)

“We mortals operate on wave lengths from the Universal, the Trinity; these are our life waves. They are distributed, one wave from each of the ruling suns. Each of our waves is on a set length or frequency; the blending of the three waves is the Power. This sets the pattern of our individual frequency. It is the source of our personality, our identity and it is as distinct and individual as our own finger-prints. “On the strength of our wave we, similar to a planet, operate by our magnetic field through the medium and receive the knowledge we need from the vast pool of wisdom. It is... View Details

Magnetic Field(s)
by Ron Loewinsohn (Author), Steve Erickson (Preface)

Organized around the idea that "you can't know what a magnetic field is like unless you're inside of it, " Ron Loewinsohn's first novel opens from the disturbing perspective of a burglar in the midst of a robbery and travels through the thoughts and experiences (both real and imaginary) of a group of characters whose lives are connected both coincidentally and intimately. All of the characters have a common desire to imagine and invent rather horrifying stories about the lives of people around them. As the novel develops, certain phrasings and images recur improbably, drawing the reader into... View Details

Magnetic Fields: A Comprehensive Theoretical Treatise for Practical Use
by Heinz E. Knoepfel (Author)

A unique resource for physicists and engineers working with magnetic fields
An understanding of magnetic phenomena is essential for anyone working on the practical application of electromagnetic theory. Magnetic Fields: A Comprehensive Theoretical Treatise for Practical Use provides physicists and engineers with a thorough treatment of the magnetic aspects of classical electromagnetic theory, focusing on key issues and problems arising in the generation and application of magnetic fields. From magnetic potentials and diffusion phenomena to magnetohydrodynamics and properties of... View Details

Magnetic Fields: Expanding American Abstraction, 1960s to Today
by Valerie Cassel Oliver (Author), Lowery Stokes Sims (Author), Erin Dziedzic (Editor), Melissa Messina (Editor)

In the history of American art, the contributions of African American artists to the development of abstraction have been largely overlooked.

Magnetic Fields aims to change this perspective by focusing on nonrepresentational work by women artists of color, presenting a more complete presentation of American abstraction than has previously been offered.

Intergenerational in scope, Magnetic Fields includes more than 20 artists born between 1891 and 1981, among them Lilian Thomas Burwell, Mildred Thompson, Candida Alvarez, Betty Blayton, Nanette... View Details

The Magnetic Fields
by André Breton (Author), Philippe Soupault (Author), David Gascoyne (Translator)

tr David Gascoyne View Details

Reconnection of Magnetic Fields: Magnetohydrodynamics and Collisionless Theory and Observations
by J. Birn (Editor), E. R. Priest (Editor)

The reconnection of magnetic fields is one of the most fascinating processes in plasma physics, responsible for phenomena such as solar flares and magnetospheric substorms. The concept of reconnection has developed through recent advances in exploring the magnetospheres of the Sun and Earth through theory, computer simulations and spacecraft observations. The great challenge in understanding it stems from balancing the large volumes of plasma and magnetic fields involved with the energy release with the physical mechanism which relies on the strongly localized behavior of charged particles.... View Details

NOW 2 kNOW Electro-Magnetic Fields
by Dr. T G D'Alberto (Author)

You're taking a challenging EM Fields course or simimlar while balancing umpteen other classes and maybe even a job. Your chief concern is to figure out, in the shortest time possible, how to successfully do the homework and exam problems. So, let’s get to it. The main stumbling blocks that trip up most students are conquered by a three-time teaching assistant to this course at Cornell. Get the help those students got! From a review of vector calculus to descriptions of the physics behind the math to detailed examples, this book is a must-have companion to any course addressing EM Fields.... View Details

Magnetic Fields' 69 Love Songs: A Field Guide (33 1/3)
by LD Beghtol (Author), Ken Emerson (Introduction)

A fully illustrated oral history of the Magnetic Fields' 1999 triple album, 69 Love Songs - an album that was afforded "classic" status by many almost as soon as it was released. LD Beghtol's book is chatty, incestuous, funny, dark, digressive, sexy, maddening, and delightful in equal measures. It documents a vital and influential scene from the inside, involving ukuleles and tears, citations and footnotes, analogue drum machines, and floods of cognac. Oh, and a crossword puzzle too.

The centre of the book is the secret history of these tuneful, acerbic, and sometimes... View Details

The Automatic Message, the Magnetic Fields, the Immaculate Conception (Atlas Anti-Classics)
by Andre Breton (Author), Philippe Soupault (Author), Paul Eluard (Author), David Gascoyne (Translator), Antony Melville (Translator), Jon Graham (Translator)

This book collects together the two most vital "automatic" texts of Surrealism. Breton’s prefatory essay The Automatic Message relates this technique to the underlying concepts and aesthetic of the Surrealist movement.

The Magnetic Fields (1919) was the first work of literary Surrealism and is thus one of the foundations of modern European thought and writing. This authorised translation is by the poet David Gascoyne, himself a member of the group and a friend of both authors.

The Immaculate Conception (1930) traces the interior and exterior life of man from Conception and... View Details

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

The Person You Become
Over the course of our lives, we shed parts of our old selves, embrace new ones, and redefine who we are. This hour, TED speakers explore ideas about the experiences that shape the person we become. Guests include aerobatics pilot and public speaker Janine Shepherd, writers Roxane Gay and Taiye Selasi, activist Jackson Bird, and fashion executive Kaustav Dey.
Now Playing: Science for the People

#478 She Has Her Mother's Laugh
What does heredity really mean? Carl Zimmer would argue it's more than your genes along. In "She Has Her Mother’s Laugh: The Power, Perversions, and Potential of Heredity", Zimmer covers the history of genetics and what kinship and heredity really mean when we're discovering how to alter our own DNA, and, potentially, the DNA of our children.