What would ocean basins look like, if we drained away all of the water? Like a big bathtub, with a wide, flat bottom in the middle? Or like a round bowl, with the deepest spot at the very middle? Neither, really. Each ocean basin has a unique outline shape, but all have abundant underwater landscape features much like the continents, including mountain ranges, hills, valleys, flat plains and undersea canyons.
Global topography map of the land (warm colors and greens, with darker warm colors representing higher elevations and darker greens lower), and the oceans (blues, where darker blues represent lower undersea elevations).
This variable undersea (and on land) topography results from the dynamic nature of the planet, particularly plate tectonics. The outer shell of the Earth (the lithosphere, or "crust") is made up of numerous plates "riding" on a hot, deformable layer in the interior (the asthenosphere). As plates pull apart from one another, the upper asthenosphere melts into magma and rises upwards to fill the rift, cooling and creating new ocean crust. This new crust is relatively hot and buoyant, and rides high in the asthenosphere, forming mountains called Mid-Ocean Ridges. Check out the articles in this Nature special for more on rifting, and this Saltwater Science post to read about the unique organisms that live on hydrothermal vents near Mid-Ocean Ridges.
So, what makes the deep spots? As ocean crust moves away from the Mid-Ocean Ridges and ages, it cools and becomes denser, riding lower in the asthenosphere. In places where plates move towards one another, the old, dense ocean crust is pushed down into the asthenosphere underneath more buoyant, younger ocean crust or a continent (which are always more buoyant than ocean crust because they are made of a different rock type). This is called subduction. At subduction zones, where the downgoing plate bends and dives beneath the overriding plate, we get oceanic trenches. These are the deepest parts of the ocean.
The Mariana Trench, located in the western Pacific, is the deepest trench of all. Scientists still know little about the bottom of the ocean, mostly because it is dark and hard to get to (we can't just get down there using SCUBA gear to look around). Before last year, when James Cameron went to the bottom of this deepest part of the ocean in a custom-built submersible, it had only been visited once before. Just think of all the interesting creatures that live in the black depths, enduring water pressure more than 1,000 times that at the surface!
How do you think other topographic features, like canyons and seamounts, form under the ocean?
from Multimedia Library Collection:
Fothergill, Alastair and Andy Byatt. Deep Blue—A Natural History of the Oceans. Berlin: Greenlight Media GmbH, 2003. 35 mm, 90 min. //youtu.be/LsKnO7Ipl2M.
A visually and acoustically stunning screen event, Deep Blue took several years to film on locations all over the world. This one-of-a-kind look at our oceans is one of the most extraordinary and lavish projects ever made in the field of documentary film, magically pulling the viewer into the fascinating life pulsing beneath the surface of our seas. The journey leads from shallow coral reefs to the inhospitable coasts of the Antarctic, and from the vast reaches of the open sea to the deepest abysses of the oceans, a realm of eternal darkness. (Source: Greenlight Media GmbH)
© 2003 Greenlight Media GmbH. Trailer used with permission.
About the Environmental Film Profiles collection
Further readings:
- Beer, Tom. Environmental Oceanography. Boca Raton: CRC Press, 1997.
- Juda, Lawrence. International Law and Ocean Use Management. New York: Routledge, 1996.
- Print page to PDF
Dive into the science of the sea as we explore the physical factors that determine life underwater and along our coastlines. Available as a primary school science incursion within Australia or as a
video conference to any school around the globe!Science of the Deep Blue!
This show & workshop was specially designed for National Science Week 2020 ‘Deep Blue: innovations for the future of our oceans.’
Online Class Version
We’ve run live interactive distance programs since 2010 and are highly experienced in making online classes engaging for students on a variety of web conferencing platforms.
- All of the same curriculum points will be covered, but the activities may vary from those listed for face-to-face incursions.
- Our online classes include opportunities for students to ask questions.
- Full child protections are in place
- We usually connect to classes & homes via Zoom, however if you wish to use a different software we can work with you on getting the connection live.
If you connect with us via Zoom
- Full system requirements for Zoom here
- Each student should test their Zoom connection here.
- Once the date & time is arranged we will send you simple connection instructions (one click & you’re in!)
Quick Links
Australian ACARA Content Outcomes: Australian National Curriculum Mapping for all our science workshops & shows
NSW Science Syllabus Content: A student: STe-5PW-ST STe-3LW-ST
observes the way objects move and relates changes in motion to push and pull forces
explores the characteristics, needs and uses of living things
ST1-8PW-S
describes
common forms of energy and explores some characteristics of sound energy
ST2-4LW-S
compares features and characteristics of living and non-living things
ST2-6MW-S
describes how adding or removing heat causes a change of state
ST2-8PW-ST
describes the characteristics and effects of common forms of energy, such as light and heat
ST2-9PW-ST
describes how contact and non-contact forces affect an object’s motion
ST3-4LW-S
examines how the environment
affects the growth, survival and adaptation of living things
ST3-6MW-S
explains the effect of heat on the properties and behaviour of materials
ST3-8PW-ST
explains how energy is transformed from one form to another
ST3-9PW-ST
investigates the effects of increasing or decreasing the strength of a specific contact or non-contact force
NSW K – 10 Science Syllabus mapping for all our incursions
Print a PDF which details K to 6 mapping of all our science visits
Science Show Demonstrations
Light attenuation
What happens to light as we go deeper?
Under pressureHow does pressure change as you descend into the ocean?
Colourful currentsHow do heat and salinity affect ocean currents?
EcholocationWe look at how whales & dolphins hunt prey
It glows!How is luminescence used by some organisms underwater?
Science of SCUBADivers avoid decompression sickness... how & why?
Ocean acidificationCorals can't handle big changes in pH. How is this a problem now?
HydropowerWe can harness the energy of the waves!
Weird sealifeWe look at the diversity of life underwater
Whale snot samplingSeriously, this is a thing! Using drones in current research
Fresh vs salt waterHow much freshwater is there really in the world?
Cleaning our oceansHow are scientists & engineers combating pollution in our oceans?
Feedback about this marine science school show
Requirements
- Appropriate for Years K to 6 with a maximum of 240 students per science show
- Access to 2 electrical power sockets and 3 tables
- Chairs are not required
- Duration 60 minutes, set up time 45 minutes and pack up time 45 minutes
- Ability to darken the room for some of the demonstrations
- *Some science experiments may be varied depending on the age of the attending audience
During Social Distancing – Contact us
and
we’ll tailor a program to suit both your school and the State’s social distancing requirements. Further details here