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September GeoRoundUp: the best of the Earth sciences from around the web

September GeoRoundUp: the best of the Earth sciences from around the web

Drawing inspiration from popular stories on our social media channels, major geoscience headlines, as well as unique and quirky research, this monthly column aims to bring you the latest Earth and planetary science news from around the web.

Major stories

Latest IPCC report puts the oceans and cryosphere in focus

Last month the United Nations’ Intergovernmental Panel on Climate Change (IPCC) released a special report that details the current status of the oceans and icy regions of the planet, and assesses how these parts of the Earth will fare as the climate changes. The Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC for short) also projects how future changes to Earth’s oceans and ice will impact the global population.

“The open sea, the Arctic, the Antarctic and the high mountains may seem far away to many people,” said Hoesung Lee, Chair of the IPCC. “But we depend on them and are influenced by them directly and indirectly in many ways – for weather and climate, for food and water, for energy, trade, transport, recreation and tourism, for health and wellbeing, for culture and identity.”

The 1,170-page report is packed with scientific details that illustrate how the environment is responding to climate change and what our world may likely look like under different carbon emission scenarios. We’ve listed just a few of the report’s findings here:

  • “Small glaciers found in high mountain environments are projected to lose more than 80% of their current ice mass by 2100 under high emission scenarios.”
  • “Even if global warming is limited to well below 2°C, around 25% of the near-surface (3-4 meter depth) permafrost will thaw by 2100.”
  • “While sea level has risen globally by around 15 cm during the 20th century, it is currently rising more than twice as fast – 3.6 mm per year – and accelerating.”
  • “Sea level rise will increase the frequency of extreme sea level events, which occur for example during high tides and intense storms. Some island nations are likely to become uninhabitable due to climate-related ocean and cryosphere change.”
  • “Marine heatwaves have doubled in frequency since 1982 and are increasing in intensity.”

The key message of SROCC is that the world’s oceans are becoming warmer, more acidic and less productive, while melting glaciers and ice sheets are causing the sea level to rise. While we are already experiencing the consequences of these environmental changes, their future severity and impact on society is dependent on how much we reduce our greenhouse gas emissions, protect and restore ecosystems, manage our natural resource use, and plan for related risks.

Want to learn more about SROCC? You can check out Carbon Brief’s explainer piece that delves further into the details.

Hurricane-heavy September

The Atlantic hurricane season is usually the most active during the month of September, and this year several powerful cyclones have inflicted heavy damage on a number of coastal communities.

Hurricane Dorian destruction in Bahamas on September 2, 2019. (U.S. Coast Guard photo courtesy of Coast Guard Air Station Clearwater)

Last month, Hurricane Dorian broke records as the strongest cyclone of the season so far, and the second strongest Atlantic hurricane on record, with sustained winds reaching 300 km an hour. In its early stages, Dorian hit the Windward Islands and the US Virgin Islands, but it made the biggest impact on the Bahamas as a Category 5 hurricane. For more than 36 hours, the storm slowly dragged across the Great Abaco and Grand Bahama islands, unleashing severe wind, rain and storm surge. The American Red Cross reported that more than 13,000 houses (nearly half of the islands’ residences) were destroyed as a result. The official death toll across the country is 56, and at least 600 people are still reported missing as of 27 September.

Another notable September storm includes Tropical Storm Imelda. While Imelda’s winds were relatively slow (65 km an hour), the storm was the seventh-wettest storm on record in the United States, releasing more than a metre of rain onto southeast Texas. At least two people died from the event, and more than 1,000 high-water rescues and evacuations were made.

Hurricane Lorenzo is the latest storm to catch media attention. The storm reached Category 5 status in the central Atlantic on 28 September and was listed as the strongest hurricane on record this far north and east in the Atlantic basin. The US National Hurricane Center has reported that the storm, now a Category 1 hurricane, is passing through Portugal’s Azores Islands and is projected to make its way north to Ireland and the UK by the end of the week. While the storm’s intensity has weakened, the hurricane is still very dangerous. In the Azores Islands, Ireland and the UK, local authorities and residents have been preparing for severe weather conditions, including heavy rain and strong wind.

This graphic shows an approximate representation of coastal areas under a hurricane warning (red), hurricane watch (pink), tropical storm warning (blue) and tropical storm watch (yellow). The orange circle indicates the current position of the center of the tropical cyclone. The black line, when selected, and dots show the National Hurricane Center (NHC) forecast track of the center at the times indicated. (Credit: NOAA National Hurricane Center)

Many scientists estimate that, as the climate changes, hurricanes and storms will likely be slower, wetter and more intense.

What you might have missed 

Is ‘The Blob’ back? 

Last month news outlets have reported that a large expanse of the northeast Pacific Ocean has been experiencing unusually warm temperatures, in some places as much as 3°C higher than average records. Stretching from the Gulf of Alaska to the Hawaiian Islands, the marine heatwave is currently the second largest on record in this region in the last 40 years.

The US National Oceanic & Atmospheric Administration noted that the current heatwave resembles the early stages of ‘The Blob,’ a massive heatwave that first formed in 2014 and persisted for three years. This earlier heatwave was connected to several ecological disturbances, including large harmful algal blooms, whale entanglements, coral bleaching, sea lion malnourishment, and many fishery disasters. Scientists fear that if this new heatwave does not dissipate soon, the event could lead to similar consequences.

Sea surface temperature anomaly maps show temperatures above normal in orange and red. (Credit: NOAA)

An icy expedition

Also last month, an international team of polar scientists have launched the largest Arctic research expedition in history. On 20 September, the German research vessel Polarstern set off on a journey to the Arctic, where it will spend an entire year trapped in sea ice, allowing researchers to observe the region’s climate system. The project, known as MOSAiC (Multidisciplinary Drifting Observatory for the Study of Arctic Climate), will involve more than 300 scientists from 19 countries.

The vessel is expected to move with the natural ice drift towards the Atlantic as the year progresses, collecting valuable information on the Arctic atmosphere, sea ice, ocean, ecosystems and biogeochemistry. “We will go and do science wherever the ice might carry us,” said chief scientist Markus Rex, an atmospheric scientist at the Alfred Wegener Institute, to Nature News & Comment. Researchers hope that the data will give an updated comprehensive look into the current state of the Arctic, allowing climate models to make better estimations of the region’s future.

Other noteworthy stories

The EGU story

This month, we have launched a short survey for EGU members to provide input on what they value from EGU, the results of which will help ensure that we remain responsive to what our members want. This is particularly important in a member-led organisation like the EGU. If you are an EGU member, we’d ask you to take 5-10 minutes to give feedback on EGU and its activities.

In General Assembly related news, we have opened applications for the third edition of our Artists in Residence programme. The programme is most attractive for scientist-artists, especially those already familiar with, and interested in, the EGU General Assembly. Applications are accepted until 1 December.

Finally, a note from the EGU Executive Secretary Philippe Courtial: “After 8 successful years at the EGU office, EGU Media and Communications Manager Bárbara Ferreira has decided to give a new orientation to her career. We would like to thank her for her tireless efforts and we wish her all the best for her future career.”

And don’t forget! To stay abreast of all the EGU’s events and activities, from highlighting papers published in our open access journals to providing news relating to EGU’s scientific divisions and meetings, including the General Assembly, subscribe to receive our monthly newsletter.

Mapping Ancient Oceans

Mapping Ancient Oceans

This guest post is by Dr Grace Shephard, a postdoctoral researcher in tectonics and geodynamics at the Centre of Earth Evolution and Dynamics (CEED) at the University of Oslo, Norway. This blog entry describes the latest findings of a study that maps deep remnants of past oceans. Her open access study, in collaboration with colleagues at CEED and the University of Oxford, was published this week in the Nature Journal: Scientific Reports. This post is modified from a version that first appeared on the CEED Blog.

Quick summary:

There are several ways of imaging the insides of the Earth by using information from earthquake data. When these different images are viewed at the same time, a new type of map allows geoscientists to identify the most robust features. These deep structures are likely the remains of extinct oceans, known as slabs, that were destroyed hundreds of millions of years ago. The maps are computed at different depths inside the Earth and the resulting slabs can be resurrected back to the surface. Along with a freely available paper and website, the analysis yields new insights into the structure and evolution of our planet in deep time and space.

Earth in constant motion

The surface of the Earth is in constant motion and this is particularly true of the rocks found under the oceans. The crust – the outermost layer of the planet – is continually being formed in the middle of oceans, such as the Mid-Atlantic Ridge. In other places, older crust is being destroyed, such as where the Pacific Ocean is moving under Japan. A third type of locality sees the crust shifted along laterally, such as the San Andreas Fault in San Francisco. These three types of locations are often referred to as plate boundaries, and they connect up to divide the Earth’s surface into tectonic plates of different sizes and motions.

Where plates plunge into the mantle are termed subduction zones (red lines Figure 1, below). The configuration of these subduction zones has changed throughout geological time. Indeed, much of the ocean seafloor (blue area in Figure 1) that existed when the dinosaurs roamed the Earth has long since been lost into the Earth’s mantle and are now known as slabs. The mantle is the domain beneath the outer shell of our planet and extends to around 2800 km depth, to the boundary with the core.

The age and fabric of the seafloor contains some of the most important constraints in understanding the past configuration of Earth. However, the constant recycling of oceans means that the Earth’s surface as it is today can only tell us so much about the deep geological past – the innards of our planet hold much of this information, and we need to access, visualize, and disseminate it.

Figure 1. A reconstruction of the Earth’s surface from 200 Million years ago to present day in jumps of 10 Million years. Red lines show the location of subduction zones, other plate boundaries in black, plate velocities are also shown. Continents are reconstructed with the present-day topography for reference. Based on the model of Matthews et al. (2016; Global and Planetary Change). Credit: G Shephard (CEED/UiO) using GPlates and GMT software.

Imaging the insides

Using information from earthquake data, seismologists can produce images of the Earth’s interior via computer models – this technique is called seismic tomography. Similar to a medical X-ray scan that looks for features within the human body, these models image the internal structure of the Earth. Thus, a given seismic tomography model is a snapshot into the present-day structure, which has been shaped by hundreds of millions to billions of years of Earth’s history.

However, there are different types of data that can be used to generate these models and different ways they can be created, each with varying degrees of resolution and sensitivity to the real Earth structure. This variability has led to dozens of tomographic models available in the scientific arena, which all have slightly different snapshots of the Earth. For example, deep under Canada and the USA is a well-known chunk of subducted ocean seafloor (see ‘slab’ label in Figure 2). A vertical slice through the mantle for three different tomography models shows that while overall the models are similar, there are some slight shifts in its location and shape.

Importantly, seismic waves pass through subducted, old, cold oceanic plates more quickly than they do through the surrounding mantle (in the same way that sound travels faster through solids than air). It follows that these subducted slabs can be ‘imaged’ seismically (usually these slab regions show up as blue in tomography models such as in Figure 2 and as shown in this video by co-author Kasra Hosseini. The red regions might represent thermally hot features like mantle plumes).

Figure 2. Vertical slices through three different seismic tomography models under North America and the Atlantic Ocean (profile running from A to B). The blue region outlined by black dashed line is related to the so-called Farallon slab. While it is imaged in all three models the finer details of the slab geometry and depth are different. Model 1 is S40RTS (Ritsema et al., 2011), 2 is UU-P07 (Amaru, 2007) and 3 is GyPSum-S (Simmons et al., 2010).

For other geoscientists to utilize this critical information, for example to work out how continents and oceans moved through time, requires a spectrum of seismic tomography models to be considered. But several limiting questions arise:

Which tomography model(s) should be used?

Are models based certain data types more likely to pick up a feature?

How many models are sufficient to say that a deep slab can be imaged robustly?

Voting maps of the deep

To facilitate solutions to these questions, a novel yet simple approach was undertaken in the study. Different tomography models were combined to generate counts, or votes, of the agreement between models – a sort of navigational guidebook to the Earth’s interior (Figure 3).

Figure 3. An interactive 360° style image for the vote map at 1000 km depth. The black and red regions highlight the most robust features (high vote count = likely to be a subducted slab of ocean) and the blue regions are the least robust areas (low vote count). Coastlines in black for reference. Image: G Shephard (CEED/UiO) using 360player (https://360player.io/) and GMT software. More depth slices and options can be also imaged at our website.

A high vote count (black-red features in Figure 3) means that an increased number of tomography models agree that there could be a slab at that location. For the study in Scientific Reports the focus was on the oldest and deepest slabs, but the process can be undertaken for shallower and younger slabs, and for other features such as mantle plumes. The maps show the distribution of the most robust slabs at different depths – the challenge is to now try and verify the features and potentially link them to subduction zones at the surface back in time.

One way to achieve this is to assume that a subducted portion of ocean will sink vertically in the mantle, and then to apply a sinking rate to connect depth and time. This enables pictures that link the surface and deep Earth, like the cover image, to be made. A sinking rate of say, 1.2 centimeters per year, means that a feature that existed at the surface around 100 Million years ago might be found at 1200 km depth.

Many studies have started to undertake a similar exercise on both regional and global scales. However, because these vote maps are free to access, showcase a lot of different models and can be remade with a sub-selection of them, they serve as an easy resource for the community to continue this task.

Secrets in depth

A bit like dessert-time discussions about the best way to cut a cake, so too are the ways of imaging and analyzing the Earth (Figure 4). Do you slice it horizontally and see things that might correspond to the same age all over the globe? Or slice vertically from the surface to see a spectrum of ages (depths) at a given location? Or perhaps a 3-D imaging would be most insightful? Whichever choice is made for the vote maps, many interesting features are displayed.

Figure 4. Vote maps visualized using alternative imaging options on a sphere. Credit: G Shephard (CEED/UiO) using GPlates software

By comparing the changes in vote counts with depth, some intriguing results were found. An apparent increase in the amount of the slabs was found around 1000-1400 km depth. This could mean that about 130 Million years ago more oceanic basins were lost into the mantle. Or perhaps there is a specific region in the mantle that has “blocked” the slabs from sinking deeper for some period of time (for example, an increase in viscosity).

The vote maps and their associated depth-dependent changes hold implications on an interdisciplinary stage including through linking plate tectonics, mantle dynamics, and mineral physics.

Of course, the vote maps are only as good as the tomography models that they are comprised of – and by very definition, a model is just one way of representing the true Earth.

A resource for the community

Having accessed a variety of tomography models provided by different research groups or data repositories, this study was facilitated using open-source software (Generic Mapping Tools and GPlates).

An important component of reproducible science and advancing our understanding of Earth is to make datasets and workflows publicly available for further investigations.

An online toolkit to visualize seismic tomography data is being developed by the co-authors and a preliminary vote maps page is already online. Here, vote maps for a sub-selection of tomography models can be generated, including with a choice in colour scales and with overlays of plate reconstruction models. More functionality will soon be available – so watch this space!

By Grace Shephard, a postdoctoral researcher in tectonics and geodynamics at the Centre of Earth Evolution and Dynamics (CEED)

Contact information for more details: Grace Shephard – g.e.shephard@geo.uio.no

Full reference to the article, freely available to the public:

Amaru, M. L. Global travel time tomography with 3-D reference models,. Geol. Ultraiectina 274, 174 (2007).

Matthews, K.J. K.T. Maloney, S. Zahirovic, S.E. Williams, M. Seton, R.D. Müller. 2016. Global plate boundary evolution and kinematics since the late Paleozoic. Global and Planetary Change. v146. doi: 10.1016/j.gloplacha.2016.10.002

Ritsema, J., Deuss, A., van Heijst, H. J. & Woodhouse, J. H. S40RTS: a degree-40 shear-velocity model for the mantle from new Rayleigh wave dispersion, teleseismic traveltime and normal-mode splitting function measurements. Geophysical Journal International 184, 1223-1236, doi:10.1111/j.1365-246X.2010.04884.x (2011).

Simmons, N. A., Forte, A. M., Boschi, L. & Grand, S. P. GyPSuM: A joint tomographic model of mantle density and seismic wave speeds. Journal of Geophysical Research: Solid Earth 115, doi:10.1029/2010JB007631 (2010).

 

 

 

Geosciences Column: Three hundred years probing the deep seas

Patagonia Blues, Credit: Agathe Lisé-Pronovost (distributed via imaggeo.egu.eu)

Patagonia Blues, Credit: Agathe Lisé-Pronovost (distributed via imaggeo.egu.eu)

The depths of the deep blue have fascinated explorers, scientists and humanity for centuries. And is it any wonder? 71% of the Earth’s surface is covered by oceans teaming with riches, from unique forms of life to precious metals.Even today, there are vast regions of the ocean floors that remain unexplored and of which we know very little about. Some might argue the oceans are the last unexplored frontier on the planet.

To quote Steinar Ellefmo, an Associate Professor at NTNU’s Department of Geology and Mineral Resources Engineering, “We actually know more about the moon than the seafloor.”

The divisions of the worlds oceans. Attribution: K. Aainsqatsi, distributed via Wikipedia.org

The divisions of the worlds oceans. Attribution: K. Aainsqatsi, distributed via Wikipedia.org. Click to enlarge.

The oceans are divided into zones according to depth, temperature and how much light those depths receive. The cold and dark waters of the twilight zone and beyond continue to be the focus of much attention and fascination today. But the pursuit of understanding the ocean deep is not new; it dates back at least 400 years, if not longer.

Reconstructing the historical records of the origins of the exploration of the ocean depths is not always easy. Hampered by incomplete recording of data, poor cross referencing between studies and limited value attributed to the findings made by non-scientific sea endeavours such as fishing, historical accounts can be piecemeal. A recent paper, published in the open access journal Biogeosciences, aims to address some of these inconsistencies, as well as setting the record straight on an age-old historical misrepresentation.

How deep are the oceans and seas?

The first scientific records of attempts to measure ocean depth in the bathyal zone (defined by Gage and Tyler as depths below 200m), date back to 1521: Magellan, a Portuguese explorer who organised the first Spanish expedition to the East Indies, unsuccessfully tried to sound the ocean bottom between two pacific coral islands. It wasn’t until the 18th century that the quest for understanding the ocean floor took off in earnest.

Expedition records show that a number of 18th century explorers were, allegedly, able to sound ocean depths up to 1950m (the John Ross expedition to the Northwest Passage of the Arctic). We now know that the depths of those soundings are around half that of the depths published and likely never exceeded 1100m.

An encounter between British Royal Navy expedition, led by John Ross, and Inuit people on Baffin Bay, Greenland. The artist John Sacheuse (sometimes spelled Sackhouse) was an Inuit who acted as interpreter for Ross’s party.

An encounter between British Royal Navy expedition, led by John Ross, and Inuit people on Baffin Bay, Greenland. The artist John Sacheuse (sometimes spelled Sackhouse) was an Inuit who acted as interpreter for Ross’s party.

The problem arose from the technique employed: a line and plummet was allowed to sink to the ocean bottom and the final length of the line recorded, but divergences between the apparent and true depths plagued measurements throughout the 18th and 19th centuries. For instance, The James Clark Ross expedition (1839 -1843), sounded the ocean depth east of Brazil at 8400m, but these depths are never encounter in the region. It wasn’t until dredging became possible, and common, place that depth measurements and sampling of the sea bed saw an improvement.

Life in the bathyal zone and beyond

The aims of taking measurements of the depth of the oceans were twofold: early explorers not only wanted to know how far down our oceans extend, but also whether the waters beyond where light can penetrate could sustain life.

French naturalist François Péron proposed that the sea beds were covered by eternal ice and so the deep waters of the oceans would be unable to sustain life. On theoretical grounds, British geologist Henry de la Beche, agreed with Péron’s concept of lifeless deep ocean waters. But it was the work of naturalist Edward Forbes during the mid-1800s which really cemented the notion of an azoic layer in the oceans. While involved in sea-dredging expeditions around The British Isles and the Aegean Sea, Forbes noticed that life became increasingly sparse with greater water depth and developed the theory that ocean waters were devoid of life at depths in excess of 550m.

Basket star - Gorgonocephalus arcticus (Leach, 1819) (from Koehler 1909, pl. 9; as Gorgonocephalus agassizi; Stimpson, 1854). This is the species that was caught during the John Ross expedition.

Basket star – Gorgonocephalus arcticus (Leach, 1819) (from Koehler 1909, pl. 9; as Gorgonocephalus agassizi; Stimpson, 1854). This is the species that was caught during the John Ross expedition. From Etter and Hess, 2015. Click to enlarge.

Contrary to popular belief, the earliest recovery of deep water life was not that of the famous basket star – a branched arm, sometimes medusa-like, sea star – by John Ross in 1818. The first published record is significantly older. Specimens of upper bathyal stalked crinoid (Cenocrinus asterius) were brought up by fishing lines in the Caribbean, with specimens reaching Europe in 1761 and 1762. However, the depths at which they had been recovered were never recorded. Deep-sea fish were also recovered from the Azores, Madeira, northern Spain, Sicily and Antillean islands, but often found in shallow waters or as dead specimens floating near shore.

Cenocrinus asterius (Linné, 1767) (from Guettard, 1761, pl. 8; as “Palmier marin”). This was the first modern stalked crinoid that was described.

Cenocrinus asterius (Linné, 1767) (from Guettard, 1761, pl. 8; as “Palmier marin”). This was the first modern stalked crinoid that was described.  From Etter and Hess, 2015. Click to enlarge.

The peculiar appearance, especially in the case of the stalked crinoids, and lack of detailed records as to what depths they’d been recovered from, meant that studies of these specimens focused on their potential to be ‘living fossils’, rather than geographical distribution within the water column. Even John Ross’, now famous, basket star was neglected from much of the early 19th century literature. Not only that, the issues with accurately ascertaining the depths of soundings and the belief that organisms became entangled higher up in the water column, recovery of specimens via this method was considered far less reliable than dredging.

Had the records of earlier soundings been accurately logged and all discoveries portrayed in the literature of the time, would Forbes’ theory of a lifeless deep ocean been debunked sooner? As well as correcting the long established notion that John Ross’ basket star was the first record of deep water life, the findings of the Biogeosciences review paper highlight the importance of not uncritically following previously published synthesis of historical literature.

 

By Laura Roberts Artal, EGU Communications Officer.

 

References

Etter, W. and Hess, H.: Reviews and syntheses: the first records of deep-sea fauna – a correction and discussion, Biogeosciences, 12, 6453-6462, doi:10.5194/bg-12-6453-2015, 2015.

Gage, J. D. and Tyler, P. A.: Deep-Sea Biology: a Natural History of Organisms at the Deep-Sea Floor, Cambridge University Press, Cambridge, UK, 504 pp., 1991.

Geoscience hot topics – Part I: The Earth’s past and its origin

Geoscience hot topics – Part I: The Earth’s past and its origin

What are the most interesting, cutting-edge and compelling research topics within the scientific areas represented in the EGU divisions? Ground-breaking and innovative research features yearly at our annual General Assembly, but what are the overarching ideas and big research questions that still remain unanswered? We spoke to some of our division presidents and canvased their thoughts on what the current Earth, ocean and planetary hot topics will be.

There are too many to fit in a single post so we’ve brought some of them together in a series of posts which will tackle three main areas: the Earth’s past and its origin, the Earth as it is now and what its future looks like, while the final post of the series will explore where our understanding of the Earth and its structure is still lacking. We’d love to know what the opinions of the readers of GeoLog are on this topic too, so we welcome and encourage lively discussion in the comment section!

 

The Earth’s past and its origin

Rephrasing the famous sentence by James Hutton, i.e. the present is the key to the past, we can even say that the past is the key to the future – a better understanding of past Earth processes can help understand why and how our planet evolved to have oceans, an atmosphere, a planetary magnetic field as well as the ability to sustain life. Not only that, a greater understanding of the Earth’s past can aid in finding solutions to present day problems. A strong interdisciplinary research effort is required to delve into the Earth’s past and that makes it one of the most important geoscience hot topics, albeit very broad.

Life on Earth and the physical environment

Zircons in rocks from Jack Hills in Western Australia provide evidence of oceans 4.4 b.y. ago and of conditions that may have haboured life. The remarkable thing is that these rocks are 300 million years older than the 3.8 billion year old rocks from Greenland, which were thought to hold the oldest evidence for life on Earth, until now.

Image by Robert Simmon, based on data from the University of Maryland’s Global Land Cover Facility

Jack Hills, Western Australia. Image by Robert Simmon, based on data from the University of Maryland’s Global Land Cover Facility

These findings are no doubt very exciting, but they also go hand in hand with gaining a greater understanding about the physical environment in which these early life forms evolved. According to Helmut Weissert, President of the Stratigraphy, Sedimentology and Palaeontology Division (SSP), understanding the co-evolution of life and the physical environment in Earth’s history is one of the biggest challenges for current and future scientists. Understanding past changes of the System Earth will facilitate the evaluation of man’s role as a major geological agent affecting global material and geochemical cycles in the Anthropocene.

The work of scientists in the SSP fields on understanding how the evolution of life was affected by major climatic perturbations is particularly timely, given the ongoing debate as to whether the presence of humans on Earth is potentially driving a sixth mass extinction event. Not only that, a big research question still unanswered is how did catastrophic events during the Earth’s history also affect evolutionary rates?

Developing new models and tools which might aid investigation in these areas is at the forefront of challenges to come, along with a greater interaction between related disciplines, for instance (but of course, not limited to!) the geosciences and genetics.

A changing inner Earth

The Earth’s magnetic field is one of ingredients for the presence of life on Earth, because it screens most of the cosmic rays that otherwise would penetrate in major quantities into the atmosphere and reach the surface, being dangerous for human health.

“A recent discovery is that the absence of magnetic field would cause serious damages not only to humans through a significant increase of cancer cases, but also to plants”, say Angelo De Santis, President of the Earth Magnetism and Rock Physics Division (EMRP), “implying that geomagnetic field reversals characterised by times with very low intensity of the field, would have serious implications for life on the planet”.

Another way to understand this aspect would be to have a look at the past. One of the (many) tools which can be used to understand what our planet might have looked like in its infancy is palaeomagnetism. This is especially true when it comes to one of the biggest conundrums of the Precambrian: when did plate tectonics, as we understand them now, start?

That there was perhaps some form of plate motions in the Earth’s early life is likely, but exactly what the style of those plate motions were during the Precambrian is still highly debated. Palaeomagnetic directions measured over time are used to estimate lateral plate motions associated with modern day style plate tectonics involving subduction. If similar plate motions can be identified in rocks younger than 500Ma then they might support lateral plate motions early in the Earth’s history. This, says Angelo De Santis, is one of the most exciting areas of research within Earth magnetism.

 Earth Magnetic Field Declination from 1590 to 1990 by U.S. Geological Survey (USGS). Licensed under Public Domain via Wikimedia Commons . Click on the image to see how the field changes over time.

Earth Magnetic Field Declination from 1590 to 1990 by U.S. Geological Survey (USGS). Licensed under Public Domain via Wikimedia Commons . Click on the image to see how the field changes over time.

Not only that, studying the strength of the geomagnetic field (which is generated in the liquid outer core by a process known as the geodynamo) and how it changes over different time scales can give us information about the early inner structure of the planet. For instance, news of a new date for the age of the formation of the inner core, after researches identified the sharpest increase in the strength of the Earth’s magnetic field, hit the headlines recently. The findings imply that maybe some of the views Earth scientists hold about the core of the Earth might need to be revised!

Which leads us onto secular variation – the study of how the geomagnetic field changes, not only in strength but also in direction – because if the early core is different to how it was previously thought, is the understanding of secular variation also affected? The implications are far reaching, but a highlight, according to Angelo De Santis, has to be how the findings might affect how periods of large change (more commonly known as geomagnetic reversals) are understood. Therefore, it is key that the evolution of the geodynamo is better understood, so that scientists might be able to assess the possibility of an imminent excursion (a large change of the field, but not a permanent flip of the direction) or reversal.

From the inner Earth to the surface

If studying the inner depths of the Earth in the past might give us clues about the present and future of the planet’s core, so to on and above the surface the past can be the key to the future.

Geological time spiral" by United States Geological Survey - Graham, Joseph, Newman, William, and Stacy, John, 2008, The geologic time spiral—A path to the past (ver. 1.1): U.S. Geological Survey General Information Product 58, poster, 1 sheet. Available online at http://pubs.usgs.gov/gip/2008/58/. Licensed under Public Domain via Commons.

Geological time spiral by United States Geological Survey – Graham, Joseph, Newman, William, and Stacy, John, 2008, The geologic time spiral—A path to the past (ver. 1.1): U.S. Geological Survey General Information Product 58, poster, 1 sheet. Available online at http://pubs.usgs.gov/gip/2008/58/. Licensed under Public Domain via Commons.

Present day climate change is a given, but predictions of how the face of the Earth might change as a result remain difficult to make while, at the same time, its consequences are not yet fully understood. Studying the climate of the past and how the biosphere, oceans and the Earth’s surface (including erosion and weathering processes), responded to abrupt and potentially damaging changes in Earth’s past climate provides a starting point to make forecasts about the future.

“A better time resolution of geological archives means we are able to further test present day climate, weathering and ocean models,” says SSP President Helmut Weissert.

And so, not only does the past tell us where we come from and how the Earth became the only planet in our Solar System capable of sustain complex forms of life, a better understanding of its origins and past behaviour might just help us improve the future too.

Next time, in the Geosciences hot topics short series, we’ll be looking at our understanding of the Earth as we know it now and how we might be able to adapt to the future. The question of how we develop the needs for an ever growing population in a way that is sustainable opens up exciting research avenues in the EMRP and SSP Divisions, as well as the Energy, Resources and the Environment (ERE), Seismology (SM) and Earth and Space Science Informatics (ESSI) Divisions.