L1 - Introduction and Ocean Basins Flashcards
What so great about oceans?
Where life began and continues to thrive. >70% of earths surface, 99% of all living space, 50 - 80% of all life on earth
In what conditions does life survive in?
Nearly every set of conditions
What does half of the global ocean provide?
Oxygen. Photosynthesis (primary production) by phytoplankton, mangroves, seagrass, green algae
What does the global ocean do?
Sequester (stores) Carbon, regulate the planet’s climate
Why and how do humans depend on the global ocean?
The ocean offers ecosystems services ; fishing, aquaculture, energy, tourism, transport, medicine, coastal defence, culture, wellbeing, physical materials
What are 4 main oceans?
Arctic, Pacific, Atlantic, Indian
What are oceans?
Connected they’re not homogenous
What does the oceans connectivity means?
It means problems are also shared
What is there between oceans and continents?
A geological distinction
What is the clear geological distinction between oceans and continents?
In rock, density, thickness, age, colour, elements
Geological distinction between oceans and continents - Oceanic crust?
Basalt (rock), ~3.0 g cm^-3 (density), 5km (thickness), geologically young (<200 My) (age), dark (colour), iron, magnesium (elements)
Geological distinction between oceans and continents - Continental crust?
Granite (rock), ~2.7 g cm^-3 (density), 20-50km (thickness), can be very old (age), light (colour), sodium, potassium, calcium, aluminium (elements)
What does the earth surface comprise of?
Crust, upper mantle, lower mantle, outer core, inner core
What is the density of the continental crust?
lower density
What is the density of the ocean crust?
higher density
What is the lithosphere?
crust & uppermost mantle (tectonic plates)
Where is the asthennosphere is what are its characteristics?
In the upper crust, it is weak and allows plates to move
What was the continent and ocean like 200 million years ago?
one continent and one sea
What is constantly changing?
The surface of the earth is constantly changing and moving - on a very long timescale
What are tectonic plates?
The crust and the upper part of the mantle - the lithosphere, broken into tectonic plates - move as a single unit. Different plates contain continental crust, oceanic crust or both. The lithosphere floats on a denser, more plastic layer of upper mantle (the asthenosphere)
What does tectonic plate movement cause?
Oceanic ridges and trenches
What creates oceanic ridges?
Sea-floor spreading
What causes the formation of deep trenches?
Plate collisions
What geological activity is concentrated at mid-ocean ridges and boundaries?
Volcanoes, Deep-focus earthquakes
What two regions can the sea floor be divided into?
The continental margins, The deep-sea floor
What are the continental margins of ocean basins?
The boundaries between continental and oceanic crust
Continental margins of ocean basins - Continental shelf?
8% of the ocean’s surface area, but the biologically richest parts of the ocean
Continental margins of ocean basins - Shelf break?
Usually depths of 120-200, but can be up to 400m deep
Continental margins of ocean basins - Continental slope?
Deep submarine canyons often cut across the slope to its base (3,000 - 5,000 metres), channeling sediments from the continental shelf to the deep sea
Continental margins of ocean basins - Continental rise?
Sediments building up at the base of the slope
How can continental margins of ocean basins be considered?
Active or passive
What is an deep-ocean basin?
Abyssal plain
What are Deep-Ocean basins?
Most of the deep-sea floor (the abyssal plain) is 3,000 - 5,000 metres deep. Relatively flat, but with features such as submarine channels, low abyssal hills, plateaus, rises, seamounts, volcanic islands and more. Supports a surprising variety of life
