earth science

Tikitere Graben

Tikitere Graben is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tikitere Graben rather than just read about it. In short: The Tikitere Graben is an intra-rift graben in the North Island of New Zealand that contains the Ohau Channel, which drains Lake Rotorua into Lake Rotoiti with a minimal drop between the lakes. Geography The Ohau Channel ultimately allows both lakes to drain into the Kaituna River through drainage that is also associated with the graben.

Key takeaways

Tikitere Graben belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tikitere Graben to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tikitere Graben from memory before moving on to harder problems.

Reference excerpt

The Tikitere Graben is an intra-rift graben in the North Island of New Zealand that contains the Ohau Channel, which drains Lake Rotorua into Lake Rotoiti with a minimal drop between the lakes.

Geography The Ohau Channel ultimately allows both lakes to drain into the Kaituna River through drainage that is also associated with the graben. The Tikitere Graben also is associated with the geothermal tourist attraction of Hell's Gate and the western aspects of Lake Rotoiti.

Ecology From the 1950s onward the water quality of Lake Rotoiti deteriorated due to drainage into the lake via the Ohau Channel of water from Lake Rotorua that had high phytoplankton and nutrient concentrations. In July 2008 a wall was completed that directed the outflow of the Ohau Channel towards the Okere Arm in Lake Rotoiti, with the aim of reducing water mixing in Lake Rotoiti before outflow into the Kaituna River. The wall meet its design parameters. As of 2020, because of perhaps this measure amongst others, there is stable water quality in Lake Rotoiti. The Ohau Channel itself is regularly monitored for fish biodiversity with reducing abundance of the common bully in the period between 2007 and 2012. This continued into 2016 with changes observed in other river fish.

Geology The Tikitere Graben is subsiding at 0.2 cm/year (0.079 in/year) and has destroyed the Rotorua Caldera rim at this point, so providing the current natural outlet for Lake Rotorua. The graben is a tectonic intra-rift graben within the Taupō Rift and is delimited by two unnamed active faults in the current active NZ fault database (#3590 and #2210). These north-west to south-east trending faults could be modelled to suggest the graben is being produced by a transtensional stress regime or as an accommodation zone between offset spreading centres. Historically some suspect that the graben did not exist, after the Rotorua Caldera forming Mamaku eruption of approximately 240,000 years ago. After this, the lake filled to a maximum elevation of 414 m (1,358 ft) above sea level. The drainage of this initial Lake Rotorua is not known, but would have been through the Tikitere Graben most of the time since. The outlet was perhaps initially through the Hemo Gap to the south of the present town of Rotorua. Whatever there has been drainage at times through the Hemo Gap, and at some stage drainage of Rotorua Lake through the Tikitere Graben became established prior to the Rotoiti eruption in the Ōkataina Volcanic Centre of 47,400 years ago. Drainage may not have been through what seems to be a very young Kaituna River gorge and a possible route far to the east beyond the present eastern end of Lake Rotoiti is suspected. It is known that after the Rotoiti eruption Lake Rotorua rose to an elevation of just over 370 m (1,210 ft) and at a later stage drained through the Tikitere Graben back into what is now Lake Rotoiti scoring an approximately 1 km (0.62 mi) wide, 60 m (200 ft) deep channel in the western arm of Lake Rotoiti to reach initially the eastern Rotoiti craters of the Haroharo caldera in the Ōkataina Volcanic Centre and then on to the sea. By about 9500 years ago dome building activity in the eastern Haroharo portions of the Ōkataina Volcanic Centre had raised Lake Rotoiti to a maximum elevation of 294 m (965 ft) so it started flowing down the Kaituna River and in due course further graben sinking resulted in both lakes having the near common outlet level of today's 280 m (920 ft).

References

Illustrations

Worked examples

Example 1 — a first encounter with Tikitere Graben

Start with the simplest possible case. Write down what Tikitere Graben claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tikitere Graben before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tikitere Graben ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tikitere Graben

In research: Tikitere Graben appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tikitere Graben in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tikitere Graben is common in secondary-school and first-year university syllabi. It links to neighbouring topics Landforms of the Bay of Plenty Region, Rivers of New Zealand, Rivers of the Bay of Plenty Region, so understanding it makes those chapters shorter.
In everyday life: Look for Tikitere Graben outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tikitere Graben in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tikitere Graben means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tikitere Graben out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tikitere Graben in simple terms?

The Tikitere Graben is an intra-rift graben in the North Island of New Zealand that contains the Ohau Channel, which drains Lake Rotorua into Lake Rotoiti with a minimal drop between the lakes. Geography The Ohau Channel ultimately allows both lakes to drain into the Kaituna River through drainage…

Why does Tikitere Graben matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tikitere Graben?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tikitere Graben.