Page 336 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

depth,
319
(k). The temperature
(AT) over a
(q) according to the geothermal
with
Surface
temperature
temperature
Conductivity

Earth’s
(aver-
thin plate of thermal conductivity
m7!°c"!)
in
increase
rocks
Across
2.6,
the change in
2.8
3.4
28
1.8
21
3.7
3.3
2.3
Thermal
of selected
top (T,). b) For constant
Flow
(W
rate
region.
a
Heat
knowledge of k,T,.and
Earth's surface at
the
conductivity
of rocks in
Sandstone
Limestone
across a
Rock
Andesite
Rhyolite
Gabbro
Granite
Diorite
Basalt
the
(k)
flows through
Shale
1990).
Thermal
at
conductivity
a) Transfer of heat
is hotter than
from
Jessop,
be determined
Heat
Sedimentary
thermal
10.1
from
(T,)
(Az).c)
Igneous
Heat flow.
TABLE
plate
the
ages
flow [q(z)] can
in depth
and
bottom of the
(dT /6z)
10.11
small change
-
gradient
the heat
FIGURE
at the
3.0 Amphibolite Metamorphic 3.5 Serpentinite ~ 5.0 Quartzite Flow Heat of Measurement is flow heat that illustrates 10.13 Fig. differ- at temperature the taking by measured core piston a in depths ent If (aT /dz). gradient geothermal the drillhole, yielding or average an flow heat the regio
be (T)). at the to 2 signifi- rocks
can conducted m7’) 10.11b), flow in from higher geother- with
surface is surface (W (Fig. heat downward range be can
its energy plate the (heat flow) (thermal conductivity) from
to temperature of the downward z 10.11c),; surface rocks quartzite) constant, regions 10.12b).
interior Heat lowest top °C"!) surface as: depth (Fig. surface heat the most results is (Fig.
Earth’s 10.11a). the a) the through m7? (W (°C) plate (°C) the of depth downward) to surface z. ass & N ‘ depth Earth's conduct from for (sandstone. flow heat gradient flow
al
=
SURFACE from (Fig. model to (T>) alte h r( area, plate the of the plate the of (m). from function (lay (positive the from depth to = Wl q(z) A730 E\s with (8T/dz) = k across outward to region increases conductivities quartz in geothermal heat higher
~~
a
il
EARTH’S conduction by plate temperature 1 unit flow, per conductivity of surface the base the plate temperature in a as - oi) z depth temperature surface the Az: small lim az temperature q flows the in temperature (geothermal gradient). thermal rich rocks conductivity, higher the If have
Flow flows simple a highest at al the of increase expressed at in from very in thus: heat rocks of which that for thermal 10.12a). conductivity
Heat ACROSS heat through with of heat rate thermal temperature temperature thickness linear be can flow heat change distance for increase is that rate ability at rate region shows 10.1 Values “i given (Fig.
10 Equation that Jevel lo: = q = k = T, = T, = h a is flow = = AT = Az limit, the constant surface = q = k = Table °C™!. higher. a For gradient thermal
Chapter FLOW Flow rate The envisioned the from according where: there If heat the where: q(z) Taking For Earth’s where: aT/dz m7! W 3 cantly mai of higher
318 HEAT Heat