Seismologists use triangulation to locate earthquake epicenters. They measure the time difference between when P-waves and S-waves from an earthquake arrive at multiple seismic stations. These time differences are used to calculate the distance from each station to the epicenter. Circles are drawn around each station representing these distances, and the point where all the circles intersect indicates the epicenter location. The continental drift theory proposes that the continents were once joined together before drifting apart. Evidence for this includes matching coastline shapes, matching fossil distributions, and matching rock formations between continents now separated by oceans.

1. LOCATING AN EARTHQUAKE
& CONTINENTAL DRIFT
THEORY
LESSON 4 and 5

2. How does a
seismologist determine
the location of the
epicenter of an
earthquake if it is too
far from the seismic
station?

3. TRIANGULAT
ION METHOD
When an earthquake
occurs, seismic waves
radiate out from the
focus and cause
vibrations on the earth’s
surface.

4. SPEED
P-waves travel at a rate
of 6km/s while S-waves
travel at 4km/s.

5. Time Lag
Difference between the arrival of
P-waves and S-waves at the
seismograph station.
D =
𝑻𝒅 (𝒔)
𝟖 𝒔𝒆𝒄𝒐𝒏𝒅𝒔
x 100km
At each station, we can draw a
circle on a map that has a
radius equal to the distance to
the epicenter from each station.
The three circles will intersect at
a point that locates the
epicenter.

6. PROBLEM SOLVING D =
𝑻𝒅 (𝒔)
𝟖 𝒔𝒆𝒄𝒐𝒏𝒅𝒔
x 100km
Recording Station Time difference Distance of the station to
the epicenter
Puerto Princesa 32 seconds 400km
Batangas 44.8 seconds 560km
Davao 38.4 seconds 480km

7. Continental
Drift
Theory
Has the Earth always
looked the way it is now?

8. Evidences of the
continental drift
theory
• THE JIGSAW FIT. Continents
were once one in their
shapes. The edge of the
different continents fit the
edge of another. For instance,
South American and West
African coastlines show the
best jigsaw fit.
• FOSSIL EVIDENCE.
Glossopteris was a woody,
seed-bearing shrub or tree.
Fossils of this plant are found
in Australia, South Africa,
South America, India and
Antarctica.

9. Evidences of the
continental drift
theory
• ROCK EVIDENCE. The broad
belts of rocks and mountains
of South America and Africa
line up perfectly as if they
were once a long mountain
range.
• COAL DEPOSITS EVIDENCE.
Looking at the current
location of Antarctica, living
things could barely survive
there now. If scientists found
coal deposits there, it could
mean that Antarctica might
have been closer before to
the Equator where it had a
warmer climate and could
sustain life.