Sea floor rock samples will reveal their origin so we can understand how they
have been extruded after the partial or total melting of material rising from depths
[30 km. Upon decompression, during their ascent to shallower depths, the minerals forming the mantle will be fused. Since each mineral forming the rocks is
sensitive to changes in temperature and pressure, we can study these minerals to
infer their original depths and the extent of their melting before they were erupted
on the sea floor.
The relative abundance of different rock types encountered on the ocean floor
may not reflect the absolute quantity of any particular type. The fact that we do not
have easy access to deep-seated formations means we are limited to observations
of just the thin veneer of the Earth’s crust, with the exception of areas such as
fracture zones where the crust has been sliced and uplifted to expose more deepseated rock formations. Regions where this type of material is most likely to reach
the sea floor are magma-starved areas where volcanic activity is lacking or limited.
Such areas are found on slow spreading ridge systems, which are preferential
zones for exposing the deep-seated rocks from the Earth’s mantle. Ocean drilling
operations are also used to probe the Earth’s interior in order to sample different,
deeper formations.
Rocks: A Combination of Several Basic Minerals
A mineral is a natural, inorganic compound with an orderly internal chemical
structure and physical properties that cause it to assume a specific crystalline form.
The fascinating aspect of the minerals forming the Earth’s rocks is that they are
basically composed of atoms of just a few different elements, all of which could be
considered as being the building blocks of our planet. The different elements are
bonded together to form a mineral lattice. Each individual crystalline lattice has a
regular arrangement of elements constructing a network or a space lattice. Each
element in the lattice is composed of atoms with their specific weight, electric
charges and radii. An atom is the smallest portion of an element, which can join
with another atom or several atoms to form compounds and minerals. For example
the mineral known as quartz (or silica dioxide, SiO 2 ) is formed with one atom of
silica (Si) and two atoms of oxygen (O 2 ).
The atoms and elements are bonded together due to a sharing of their electric
charges. The space lattice between the atoms has the capacity of absorbing or
releasing electrons, thus creating energy during the formation of a new compound.
Whether the space lattice releases or absorbs an electron will depend on whether it
is charged positively (so it will release an electron) or negatively (so it can absorb
an electron). The transformation or growth of a mineral lattice will occur during
partial melting and magma solidification and/or during the alteration of a rock. The
factors that govern the behavior of all the elements are their ionic radius and their
electric charges, which characterize the atomic configuration of the elements
within a lattice.
76
4 Sea Floor Rocks
have been extruded after the partial or total melting of material rising from depths
[30 km. Upon decompression, during their ascent to shallower depths, the minerals forming the mantle will be fused. Since each mineral forming the rocks is
sensitive to changes in temperature and pressure, we can study these minerals to
infer their original depths and the extent of their melting before they were erupted
on the sea floor.
The relative abundance of different rock types encountered on the ocean floor
may not reflect the absolute quantity of any particular type. The fact that we do not
have easy access to deep-seated formations means we are limited to observations
of just the thin veneer of the Earth’s crust, with the exception of areas such as
fracture zones where the crust has been sliced and uplifted to expose more deepseated rock formations. Regions where this type of material is most likely to reach
the sea floor are magma-starved areas where volcanic activity is lacking or limited.
Such areas are found on slow spreading ridge systems, which are preferential
zones for exposing the deep-seated rocks from the Earth’s mantle. Ocean drilling
operations are also used to probe the Earth’s interior in order to sample different,
deeper formations.
Rocks: A Combination of Several Basic Minerals
A mineral is a natural, inorganic compound with an orderly internal chemical
structure and physical properties that cause it to assume a specific crystalline form.
The fascinating aspect of the minerals forming the Earth’s rocks is that they are
basically composed of atoms of just a few different elements, all of which could be
considered as being the building blocks of our planet. The different elements are
bonded together to form a mineral lattice. Each individual crystalline lattice has a
regular arrangement of elements constructing a network or a space lattice. Each
element in the lattice is composed of atoms with their specific weight, electric
charges and radii. An atom is the smallest portion of an element, which can join
with another atom or several atoms to form compounds and minerals. For example
the mineral known as quartz (or silica dioxide, SiO 2 ) is formed with one atom of
silica (Si) and two atoms of oxygen (O 2 ).
The atoms and elements are bonded together due to a sharing of their electric
charges. The space lattice between the atoms has the capacity of absorbing or
releasing electrons, thus creating energy during the formation of a new compound.
Whether the space lattice releases or absorbs an electron will depend on whether it
is charged positively (so it will release an electron) or negatively (so it can absorb
an electron). The transformation or growth of a mineral lattice will occur during
partial melting and magma solidification and/or during the alteration of a rock. The
factors that govern the behavior of all the elements are their ionic radius and their
electric charges, which characterize the atomic configuration of the elements
within a lattice.
76
4 Sea Floor Rocks